Systems and apparatuses for inserting an implant in intervertebral space

ABSTRACT

Systems and tools for inserting and securing an implant within the intervertebral space. An intervertebral disc implant with upper and lower bearing members with an articulation interface between the members for providing relative motion therebetween. The implant may be provided with various securing members for fixing the implant within the intervertebral space. A tool may be used to insert the implant, which includes a plurality of shiftable implant engaging members that are shiftable between non-engaging and engaging configurations to alternatively release or hold the implant.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/541,658, filed Aug. 14, 2009, which claims the benefit of U.S.Provisional Patent Application No. 61/089,283, filed Aug. 15, 2008. U.S.patent application Ser. No. 12/541,658 is a continuation-in-part of U.S.patent application Ser. No. 11/856,667, filed Sep. 17, 2007, now U.S.Pat. No. 8,597,357, which claims the benefit of U.S. Provisional PatentApplication No. 60/825,865, filed Sep. 15, 2006, and ProvisionalApplication No. 60/912,138, filed Apr. 16, 2007. Each of theaforementioned applications are incorporated herein by reference intheir entirety.

FIELD OF THE INVENTION

The invention relates to systems and apparatuses for inserting andsecuring an implant within a joint and, more particularly, to systemsand apparatuses for inserting and securing an implant in theintervertebral space.

BACKGROUND OF THE INVENTION

Joint degeneration is a common problem that can occur in a variety ofjoints throughout the human body. The condition typically is moreprevalent as the skeletal system ages and is often treated withmedications and/or physical therapy. These conservative treatmentssometimes meet only limited success. If unsuccessful, the patienttypically will continue to experience ongoing pain and limited mobility.

Often the treatment progression leads to a total joint replacement.These replacements have been performed for years in joints such as thehip and the knee. The replacement devices usually comprise some form ofa metallic structural component or endplate with an intermediatepolyethylene core. It is not unusual for replacements such as these togive 15-20 years of service before requiring some degree of revision.

In the spine, the surgical treatment of choice has been fusion for thetreatment of intervertebral disc degeneration. The spinal intervertebraldisc is arguably the most important joint in the spine and is situatedbetween the vertebral bodies. The spinal disc is comprised of a toughouter ring called the annulus, and a jelly-like filling called thenucleus. The belief has been that removing the diseased spinal disc(s)and fusing between affected levels will not make a significantdifference in the overall mobility of the spine. However, spinal fusionhas proved to cause an increase in degeneration at other vertebrallevels that must compensate for the loss of motion at the fused levelcommonly causing the patient to relapse into more pain and limitedmobility.

Recently, there has been a focus on the use of “motion preservation”implants over implants that promote spinal fusion. These motionpreserving implants, in the form of joint replacements in the spine,hope to alleviate many of the problems associated with fusion devices inthe spine. Intervertebral disc replacement devices are seen todaytypically comprising a pair of biocompatible metal plates with a polymeror elastomeric core, or a metal plate articulating on a metal plate.

Metal on metal implants have a history of failure in long term use,however, precision machining has spawned a reemergence of implants usingthese materials since it is believed that this change in manufacturinggreatly improves the wear. Regardless, the metal implants are radiopaqueand continue to frustrate surgeons due to the difficulty in imaging theaffected area. Other implants, such as those using a polymer orelastomeric core between metallic plates suffer from the same radiopaquefrustrations due to the metal components in addition to the addedcomplexities of design due to the necessity of utilizing a multitude ofmaterials for a single implant.

The prior art discloses a laundry list of biocompatible materialsincluding metals, ceramics, and polymers, that can be used for themanufacture of these implants, yet historically many of these materialshave failed when interfaced together and tested in an articulatingjoint. There is in particular an extensive history of failure whenpolymers articulate against polymers in weight bearing artificialjoints. Due to this failure history, polymer combinations have naturallybeen excluded as an acceptable self-articulating material combinationfor use in weight bearing joint replacements.

PEEK (poly-ether-ether-ketone), for example, has been suggested as anappropriate material of manufacture for use in implant devices due inlarge part to its strength, radiolucent nature, and biocompatibility.This is particularly true in structural implants having no articulatingcomponent. PEEK on PEEK has been suggested for use in low wearnon-weight bearing joints such as in finger joints. However, the priorart has been careful not to suggest self-articulating PEEK on PEEK as asuitable material combination in weight bearing joint replacementdevices due to the failure history of biocompatible polymersarticulating against themselves.

One important consideration in the design of an implant is ensuring thatthe implant remains at the implant site, and does not migrate. Migrationof the implant away from the intended implant site can cause dangerousand even fatal complications. In the case of an intervertebral implant,the close proximity of vital blood vessels, nerves, the spinal cord, andother vital tissues makes securing the implant in place a vital concern.Many different ways to secure the implant to the adjacent bone of thejoint have been proposed, including implementing protrusions or spikes,keels, screws, surface roughening, and bone-growth inducing coatings.

In one known form disclosed in Published U.S. Patent Application2007/0270961, a spinal implant is provided with deployable andretractable barbs for securing the implant to a vertebra. In oneembodiment, the barbs 130 have arcuate bodies having sharpened tips forprotruding into the vertebral bone. The barbs 130 are disposed withinrecesses 120 in the implant body 110 and rotatably mounted on pins 140.The pins 140 are disposed transversely to channel 160, such that thebarb rotates about the pin along the longitudinal axis of the channel.The barbs 130 are deployed via interaction with a rod 150 that isinserted into the channel 160 of the implant body 110. The rod 150 has asloped end for engaging the barbs 130 and causing them to rotate upwardsabout the pins 140 and into engagement with the bone.

In another form according to U.S. Patent Application 2007/0270961 shownin FIG. 5A-5D of that application, the deployable barbs take the form ofconical spikes 530 configured to be deployed into the adjacent vertebrafor securing the implant thereto. The spikes 530 have lower edges 538which engage with the tapered tip 552 of the rod 550, which propels thespikes through apertures 520 in the implant body 500. The implant isalso supplied with a lock mechanism 548 in the form of annular washersthat prevent the barb 530 from exiting the implant body 510.

One embodiment shown in FIG. 6 of U.S. Patent Application 2007/0270961is described as having a nucleus portion 650 that may comprise a balland trough arrangement to permit translational and rotational motiontherebetween. However, the figures of the application do not disclosesuch a nucleus portion, and it is believed that the implants shown anddescribed therein would be unable to incorporate such a configuration.Specifically, the implant bodies do not have sufficient materialthickness to incorporate at least a trough portion for a ball and troughconfiguration.

In addition, in the configurations of the embodiments shown in 1A-4D ofU.S. Patent Application 2007/0270961, the implant would be drawn furtherinto the intervertebral space by the deployment of the barbs due totheir shape and their axis of rotation about the pins. This pullingeffect is believed to be counteracted by the protrusions 172 disposed onthe end of the implant, such that an inner surface of the protrusionscan bias against a surface of the adjacent vertebra, thereby preventingthe implant from being pulled further into the intervertebral space.However, implants that have protrusions that extend outside of theintervertebral space are less preferred. For example, a cervical implantthat protrudes from the intervertebral space between adjacent vertebraemay come into contact with the trachea, which can cause pain ordifficulty in swallowing.

SUMMARY OF THE INVENTION

Testing in our laboratories however, told a different and unexpectedstory. In simulated weight bearing artificial joint configurations, PEEKagainst PEEK performed very favorably. PEEK articulating against PEEKdemonstrated exceptional mechanical performance and biocompatibilitycharacteristics required for load bearing artificial joints used in thehuman body and in other animals. PEEK may also be manufactured in afiber reinforced form, typically carbon fiber, which also performsfavorably against itself and against non-fiber reinforced PEEK.

Once PEEK was recognized as a viable option for self-articulation, itbecame clear that an entire articulating joint could be made from thematerial without the need for metallic structural or articulatingcomponents. This discovery substantially simplified the nature of weightbearing artificial joint replacement design and great benefits haveemerged. A partial list of these benefits include artificial jointsthat; have less components due to integrating features into the samecomponent that were previously separated due to the need for a pluralityof materials to serve the function, will last longer due to favorablewear characteristics, are substantially radiolucent, have a modulus ofelasticity closer to the bone tissue they are implanted in, and areultimately less expensive. It is important to note that less componentstypically equates to fewer modes of failure, reduced inventory, andsimplified manufacturing and assembly. Although less preferred, clearlyone may choose to keep the metallic components of an implant system andutilize PEEK on each articulating surface of the artificial joint for aPEEK on PEEK articulation.

Two piece articulating PEEK on PEEK intervertebral implants have beenpresented in earlier applications by the same inventor. These implantsperform exceptionally well for replacement of the spinal nucleus.However, many indications require implants of this nature to alsocomprise improved restraining features particularly in weight bearingapplications.

For example, there is a need for a simplified radiolucent artificialdisc device, with excellent wear characteristics and features that willsecure the device to the vertebral endplates or otherwise restrain itbetween the vertebral bodies. An artificial disc such as this would beparticularly useful as a lumbar disc replacement, and even more so as acervical disc replacement. The cervical disc is much smaller than thelumbar disc as is the space the cervical disc occupies. For at leastthis reason, a simplified design utilizing fewer parts is beneficial.

The articulating joint surfaces are preferably a combination of PEEKarticulating on PEEK, PEEK on carbon reinforced (CR) PEEK, or CR PEEK onCR PEEK. Boney integration of these implants may benefit from preparedosteo-conductive surfaces or coatings described elsewhere in thisdocument.

It is preferable that the radiolucent implant includes one or more smallradiopaque markers which will show on up an X-ray image to assist thesurgeon in positioning the implant during surgery. The preferredmaterial for these markers is tantalum. Typically these markers will beencased in predetermined locations in the implant at their periphery.Coatings which show up on imaging as a subtle outline of the implantdevice may also be used.

It is also preferable that the implants disclosed herein include a layerof osteo-conductive or osteo-inductive surfaces or coatings on thoseimplant surfaces in contact with bone or tissue that will assist insecuring the implant in a predetermined location. Typically this willoccur through boney integration of the bone with the coating or implantsurface. Examples of such coatings are hydroxyapatite, calciumphosphates such as tricalcium phosphate, or porous titanium spray.

The implant devices disclosed herein are particularly suited asintervertebral disc replacements for all or a portion of the naturalintervertebral disc. In addition, the securing members disclosed hereinare also suited for other spinal implants, such as vertebral bodyreplacements, spinal cages, and other fusion promoting implants, as wellas other known motion preserving implants. The devices have minimalstructural parts and are preferably manufactured from specializedmaterials that are substantially radiolucent such as PEEK orCarbon-Fiber PEEK in both their structural and joint articulatingportions.

Generally, the various systems and methods described herein allow for animplant, such as an artificial disc, to be properly sized, implanted andsecured in an intervertebral space with the disc having a bearinginterface that preserves motion between the upper and lower vertebraebetween which the disc is implanted and secured. In each form describedherein, a trial spacer may be used to assess the size of theintervertebral space so that an appropriately sized disc implant can beselected, and may also be used to assist in generating features in thevertebrae and/or end plates thereof for a securing member that holds andretains the disc implant in the intervertebral space.

An insertion tool may be used for inserting the implant within theintervertebral space between adjacent vertebrae. The insertion tool isgenerally comprised of a handle portion, an actuator, and a grippingmechanism. The gripping mechanism may include a plurality of shiftableimplant engaging members for engaging with the implant. The implantengaging members may be shiftable prongs located at a distal end of thetool that are configured to shift between a non-engaging and engagingconfigurations to alternately release and hold the implant,respectively. The prongs preferably shift vertically, i.e., eitherinferiorly or superiorly when moving between the non-engaging andengaging configurations. The tool engages with the implant at toolengaging portions of the implant, such as a tool receiving recess formedin the inner facing surface of each of the upper and lower bearingmembers. The tool may include additional features such as tab membersfor engaging with tool engaging portions on the implant bearing membersto grip the bearing members between the shiftable prongs and the tabmembers.

In some forms, the securing mechanism is associated with the implant tobe inserted into the intervertebral space therewith. After the disc andsecuring mechanism are inserted in the intervertebral space, thesecuring mechanism can be deployed into the preformed features in theadjacent vertebral bodies from the disc implant. In one form, theinsertion tool is used to engage the securing mechanism with thepreformed features in the intervertebral bodies. In another form, thesecuring mechanism is actuated directly to engage the securing mechanismwith the preformed features of the vertebral bodies.

In yet another form, the securing mechanism is inserted into theintervertebral space via the trial spacer prior to insertion of the discimplant. In this form, the securing mechanism is actuated directly to bedeployed into the features in the adjacent vertebral bodies with thedisc implant then inserted into the intervertebral space. Thereafter,the securing mechanism is actuated so as to engage both the implant andthe vertebral body for securing the implant in the intervertebral space.

In any event, the level of restraint required for a particularorthopedic application will vary. This disclosure also describesexamples of a variety of securing mechanisms or alternative featuressuitable for restraining the device in a predetermined location. Thesecuring mechanisms generally possess structure which allow for dynamicfixation of the implant. Instead of relying solely on subsidence orboney ingrowth of the bone around the features of the implant, thesecuring mechanisms actively engage the bone for immediate and reliablefixation of the implant to the vertebrae. In one embodiment, a rotatableshaft with at least one bone engaging body is disposed on the implantfor securing the implant within the intervertebral space. In anundeployed position, the bone engaging body is disposed within theimplant body. When the shaft is rotated, the bone engaging body isdeployed into the vertebra and thereby fixes the implant to the vertebrato prevent migration of the implant.

In addition, securing mechanisms according to the present invention mayincorporate designs that transmit tactile feedback to the surgeon whenthe securing mechanism is being operated. As it is very difficult forthe surgeon to visually ascertain the position of the implant and itssecuring features during operation, a surgeon will also use his hands tofeel for tactile responses transmitted from the implant and through histools. In one embodiment, the securing mechanism has a cammed surfacefor interacting with a corresponding cammed surface to cause thesecuring mechanism to be biased against the implant to provideresistance against the movement of the securing mechanism that can befelt through the surgeon's tools. In this manner, the surgeon can easilyascertain when the securing mechanism has been fully extended ordeployed. The tactile feedback features of the securing mechanism alsoprevent the securing mechanism from being over- or under-actuated, i.e.deploying the securing mechanism beyond its intended range of motion, orfailing to fully deploy the securing mechanism. This condition mayresult in improper fixation of the implant and cause damage to theimplant, spine, nerves, vascular system, or other tissue in the areaaround the spine.

Another aspect of the current invention includes securing mechanisms foran implant having anti-retraction or derotation prevention means. Somesecuring mechanisms according to the present invention are deployed orextended into the bone by actuating the securing mechanism, for example,by rotating a shaft. However, it is possible for the securing mechanismto retract or derotate back to its undeployed position over time, due toforces exerted on the implant. Thus, to prevent such an event, asecuring mechanism may be provided with means to prevent retraction orderotation. In one embodiment, derotation prevention means are providedin the form of a camming surface on the securing mechanism incombination with a corresponding camming surface on the implant. Thecamming surfaces are disposed to engage or interfere with one anotherwhen the securing mechanism is in a fully deployed position to preventderotation of the securing mechanism.

In some forms, the securing member is associated with the implant to beinserted into the intervertebral space therewith. After the disc andsecuring member are inserted in the intervertebral space, the securingmember can be deployed into the adjacent vertebral bodies from the discimplant. In one form, the insertion tool is used to engage the securingmember with the intervertebral bodies. In another form, the securingmember is actuated directly to engage the securing member with thevertebral bodies.

The securing members generally possess structure which allow for dynamicfixation of the implant. Instead of relying solely on subsidence orboney ingrowth of the bone around the features of the implant, thesecuring members actively engage the bone for immediate and reliablefixation of the implant to the vertebrae. In one embodiment, a rotatableshaft with at least one bone engaging body is disposed on the implantfor securing the implant within the intervertebral space. In anundeployed position, the bone engaging body is disposed within theimplant body. When the shaft is rotated, the bone engaging body isdeployed into the vertebra and thereby fixes the implant to the vertebrato prevent migration of the implant.

In some forms, the securing member is disposed on the upper and lowersurfaces of the upper and lower faces of the implant. However, in otherforms, the securing member may be completely submerged within the bodyof the implant such that the upper and lower surfaces with the implantare relatively smooth or flat. When the securing member is securelysubmerged within the implant, the upper and lower vertebrae need not beprepared prior to the insertion of the implant, thereby simplifying theimplantation procedure.

In another form, an implant according to the present invention may beprovided with upper and lower bearing members having respective bodiesand outer bearing surfaces. An articulation interface disposed betweenthe upper and lower bearing members allows for relative movementtherebetween. A securing member is disposed on one of the bearingmembers and has an elongate shaft portion and a bone-engaging memberdisposed on the shaft portion. The bone-engaging member is movable froman undeployed position, wherein the bone-engaging member is positionedout of engagement with an adjacent bone, and a deployed position,wherein the bone-engaging member is positioned in engagement with theadjacent bone via rotational displacement of the shaft portion. In someforms, the securing member is entirely disposed within the body of thebearing member when in an undeployed position.

In other forms, the securing member may include at least one boneengaging body disposed on the implant which is deployed into thevertebrae by the insertion of an elongate member into the implant body.The bone engaging body is disposed on the implant such that insertion ofthe elongate member causes the bone engaging body to be deployed fromits initial position to a bone engaging position. Once the elongatemember is inserted into the implant body, the bone engaging body isfully deployed and the elongate body is left within the implant to holdthe bone engaging body in the deployed position.

The securing member in some forms includes an elongate shaft portiondisposed within a channel of the bearing member and may have a pluralityof bone engaging members. The bone engaging members may be lobe membershaving bodies orientated generally transversely to the elongate shaftportion. The lobe members may have a sharpened portion for easinginsertion of the lobe member into the vertebral bone by either cuttingor piercing the bone. In other forms, the lobe members may be sized andconfigured for engaging with prepared surfaces of the vertebra, whereinthe surfaces are prepared prior to the insertion of the implant. Thevertebra may be prepared using a cutting tool to form a securing memberreceiving portion by removing bone at the implant site. The bone may beprepared by cutting grooves or channels sized and configured to receivethe securing member.

The securing member may be connected to the body of the bearing membervia a retainer member for connecting the securing member to the bearingmember body. In one form, the retainer securing member has opposing armsspaced from each other for receiving the elongate shaft member betweenthe opposing arms by a friction fit.

The upper and lower bearing members may be sized and configured to fitentirely between inner surfaces of adjacent vertebrae when thedeployable securing member is in an undeployed configuration. Thisconfiguration eases insertion of the implant, because the vertebrae neednot be prepared prior to insertion. Moreover, in a preferred form, theimplant fits entirely within the footprint of the intervertebral discspace such that the implant does not interfere with adjacent bloodvessels, nerves, tissues, digestive or respiratory tracts and the like.

In another form according to the present invention, an intervertebraldisc implant has a deployable securing member disposed on the implantbody with a projection of the deployable securing member movablyconnected to the body having a head portion with an edge for engaging abone, an actuation portion of the securing member having an actuatorengagement portion thereon. The projection is deployable between anundeployed position, wherein the projection is remote from an adjacentvertebra, to a deployed position, wherein the projection is engaged withthe adjacent vertebra through the interaction of the actuator with theprojection when the actuator is inserted along an insertion axis intothe body. The head portion of the deployable securing member is orientedin a generally transverse orientation with respect to the insertion axiswhen the securing member is in a deployed position.

The implant body has an outer bone engaging surface for non-invasivecontact with an inner surface of the adjacent vertebra and a securingmember mating portion of the implant body for mating with the securingmember which protrudes outwardly beyond the bone engaging surface. Thesecuring member mating portion comprises an elongate opening forreceiving the projection and allowing the projection to travel from theundeployed position, wherein the projection is disposed within theopening, to a deployed position, wherein the projection protrudes fromthe opening and is brought into engagement with the adjacent vertebra.The implant body may be part of a unitary implant, such as a spacerimplant, or the implant body may be one member of a multiple-partimplant, such as one of upper and lower bearing members. In a multi-partimplant, the upper and lower bearing members may be provided with upperand lower inner arcuate bearing surfaces that slidingly engage oneanother. The sliding interface between the upper and lower bearingmembers between the upper and lower inner arcuate bearing surfacesallows the bearing members to articulate with respect to one another. Inone form, the upper and lower inner arcuate bearing surfaces are sizedand configured to allow the upper and lower bearing members to rotatewith respect to one another over a range of approximately 13.7-22.5degrees in flexion and 13.8-30 degrees in extension, depending onimplant size.

In one form, the edge of the projection is deployed rostrally orcaudally into engagement with the adjacent vertebra without substantialtranslation in another direction. For example, the projection may be aspade-like lobe that is driven straight up into the vertebral bone whenit is actuated by an actuator. In other forms, the projection isconnected to a pivot shaft connected to the implant body and orientedgenerally parallel to the insertion axis such that the projection pivotsalong with the shaft in a direction transverse to the insertion axisduring deployment of the projection. Preferably, the projection andpivot shaft rotate about a pivot shaft axis parallel to the insertionaxis during deployment of the projection.

In yet another form, the securing member may take the form of a bendableelongate member that may be inserted into a securing member receivingportion of the upper or lower face of the implant. The bendable elongatemember is inserted into the securing member receiving portion whichcauses the bendable elongate member to flex or bend causing a projectionto protrude into the adjacent vertebrae thereby fixing the implant tothe vertebrae. The bendable elongate member may include preformedprotrusions that are deployed upon compression of the elongate member.

The implant preferably includes an implant body having a securing memberreceiving portion. A bendable securing member for being inserted intothe securing member receiving portion is provided to secure the implantto the vertebra. The bendable securing member is inserted into anopening of the securing member receiving portion to deploy a boneengaging member of the bendable securing member. The bone engagingmember is movable from an undeployed orientation, wherein the boneengaging member is remote from an adjacent vertebra, and a deployedorientation, wherein the bone engaging member is brought into contactwith the adjacent vertebra for securing the implant body to the adjacentvertebra. In some forms, the bone engaging member is deployed throughthe plastic deformation of the securing member upon insertion of thesecuring member into the opening of the securing member receivingportion. An abutment surface of the implant body is provided forengaging with the securing member to facilitate deformation of thesecuring member by compression of the securing member against theabutment surface. The bone engaging member may be a barb member disposedon the bendable securing member. In a preferred form, the barb member isdisposed flush to an outer surface of the securing member prior todeployment of the barb. The bone engaging member may have a structurallyweakened portion to promote plastic deformation thereof at apredetermined position to deploy the bone engaging member at a desiredlocation. The bendable member preferably comprises a plurality of boneengaging members.

In some forms, the securing member receiving portion has an opening onan outer facing surface of the implant body which permits the boneengaging member to pass through the opening and engage the adjacentvertebra. The bone engaging member is preferably predisposed to bendingat locations thereon that correspond to an opening or openings in theouter facing surface of the implant body.

BRIEF DESCRIPTION OF THE DRAWINGS

To understand the present invention, it will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of an anterior portion of the spine withtwo implants according to the present invention disposed within theintervertebral spaces;

FIG. 2 is an anterolateral perspective view of an implant according tothe present invention;

FIG. 3 is a perspective view of one part of a motion preserving implantwith a concave articulation surface according to the present invention;

FIG. 4 is a perspective view of a corresponding part of the motionpreserving implant of FIG. 3 with a convex articulation surfaceaccording to the present invention;

FIG. 5 is an anterolateral perspective view of an implant with securingmeans according to the present invention implanted within theintervertebral space;

FIG. 6 is an anterolateral perspective view of an implant with securingmeans according to the present invention;

FIG. 6A is an anterolateral perspective view of an implant componentwith securing means and inserter tool docking means according to thepresent invention;

FIG. 7 is a side view of an implant component with securing meansaccording to the present invention;

FIG. 8 is an anterolateral perspective view of an implant with asecuring mechanism according to the present invention implanted withinthe intervertebral space;

FIG. 9 is a perspective view of a bearing surface of an implantcomponent with a securing mechanism according to the present invention;

FIG. 10 is a perspective view of a securing component in the form of adeployable paddle or cam according to the present invention;

FIG. 11 is a perspective view of a bearing surface of an implantcomponent with a deployable securing mechanism according to the presentinvention;

FIG. 12 is an anterolateral perspective view of an implant with asecuring mechanism according to the present invention implanted withinthe intervertebral space;

FIG. 13 is a perspective view of an implant with a securing mechanismaccording to the present invention;

FIG. 13A is a perspective view of an implant component with a securingmechanism according to the present invention shown adjacent a vertebra;

FIG. 14 is an anterolateral perspective view of two implants with asecuring mechanism according to the present invention implanted withinthe intervertebral space;

FIG. 15 is an anterolateral perspective view of an implant with asecuring mechanism according to the present invention;

FIG. 16 is an anterolateral perspective view of two implants withsecuring mechanisms according to the present invention implanted withinthe intervertebral space;

FIG. 17 is an anterolateral perspective view of two implants withsecuring mechanisms according to the present invention implanted withinthe intervertebral space;

FIG. 18 is an anterolateral perspective view of the implant of FIG. 17;

FIG. 19 is an anterolateral perspective view of two implants withsecuring mechanisms according to the present invention implanted withinthe intervertebral space;

FIG. 20 is a perspective view of the lower implant member of FIG. 19;

FIG. 21 is a perspective view of a fastener implemented in the securingmechanism of FIG. 20;

FIG. 22 is an anterolateral perspective view of two implants withsecuring mechanisms according to the present invention implanted withinthe intervertebral space;

FIG. 23 is an anterolateral perspective view of the implant of FIG. 22adjacent a vertebrae having a groove and angled bore formed therein forengaging with the securing mechanism;

FIG. 24 is a perspective view of the implant of FIG. 22;

FIG. 25 is an anterolateral perspective view of an implant member with adeflectable stop according to the present invention;

FIG. 26 is a posterolateral perspective view of a vertebrae with aformed recess for engaging with the deflectable stop of FIG. 25;

FIG. 27 is an anterolateral perspective view of an implant with asecuring mechanism according to the present invention implanted withinthe intervertebral space;

FIG. 28 is a perspective view of the implant of FIG. 27;

FIG. 29 is a perspective view of an implant member of the implant ofFIG. 27;

FIG. 30 is an anterolateral perspective view of a vertebra with a formedrecess for interacting with a securing mechanism;

FIG. 31 is an anterolateral perspective view of two implants withsecuring mechanisms according to the present invention implanted withinthe intervertebral space;

FIG. 32 is a perspective view of a bearing surface of the lower implantmember of the implant of FIG. 31;

FIG. 33 is a top view of a vertebra end plate with grooves formedtherein for mating with the securing mechanism of the implant of FIG.31;

FIG. 34 is a perspective view of an implant component according to thepresent invention with a motion limiting component disposed on thearticulating surface;

FIG. 35 is a perspective view of the motion limiting component of FIG.34;

FIG. 36 is a perspective view of a corresponding implant component ofthe implant component of FIG. 34 with a motion limiting recess;

FIG. 37 is an anterolateral perspective view of a strut implantaccording to the present invention implanted within spine;

FIG. 38 is a lateral perspective view of the implant of FIG. 37;

FIG. 39 is an anterolateral perspective view of an implant member of theimplant of FIG. 37;

FIG. 40 is bottom perspective view of the implant member of FIG. 39;

FIG. 41 is a posterolateral perspective view of an artificial discimplant according to the present invention;

FIG. 42 is a posterolateral perspective view of the upper artificialdisc implant member of FIG. 41;

FIG. 43 is a posterolateral perspective view of the lower artificialdisc implant member of FIG. 41;

FIG. 44 is an anterolateral perspective view of a trial spacer assemblyaccording to the present invention inserted between two adjacentvertebrae;

FIG. 45 is an anterolateral perspective view of the trial spacerassembly of FIG. 44 with the upper vertebra hidden for illustrationpurposes;

FIG. 46 is an anterolateral perspective view of the trial spacerassembly of FIG. 44;

FIG. 47 is an anterolateral perspective view of the internal componentsof the trial spacer of FIG. 44;

FIG. 48 is an anterolateral perspective view of the components of FIG.47 including a spreader device disposed between the vertebrae;

FIG. 49 is a posterolateral perspective view of the trial spacerinternal components of FIG. 47;

FIG. 50 is a perspective view of the closing device of the trial spacerassembly;

FIG. 51 is an anterolateral perspective view of the artificial discimplant of FIG. 41 with the implant inserter;

FIG. 52 is an anterolateral perspective view of the implant of FIG. 41loaded in the inserter of FIG. 51;

FIG. 53 is an anterolateral perspective view of the implant of FIG. 41loaded in the inserter of FIG. 51 adjacent the intervertebral spaceprior to insertion;

FIG. 54 is an anterolateral perspective view of the implant and inserterof FIG. 53 with the upper arm of the inserter retracted from theimplant;

FIG. 55 is a side view of the implant of FIG. 41 implanted within theintervertebral space;

FIG. 56 is an anterolateral perspective view of a trial spacer assemblyaccording to the present invention;

FIG. 57 is a posterolateral perspective view of the trial spacerassembly of FIG. 56;

FIG. 58 is a anterolateral perspective view of the trial spacer assemblyof FIG. 56 with the shaft handle removed;

FIG. 59 is a posterolateral perspective view of the trial spacerassembly of FIG. 58;

FIG. 60 is an anterolateral perspective view of the shaft handle of thetrial spacer assembly of FIG. 56;

FIG. 61 is an posterolateral perspective view of the shaft handle of thetrial spacer assembly of FIG. 56;

FIG. 62 is an anterolateral perspective view of the trial spacerassembly of FIG. 56 inserted into the intervertebral space;

FIG. 63 is an anterolateral perspective view of the trial spacerassembly of FIG. 56 inserted into the intervertebral space with thehandle portion removed;

FIG. 64 is an anterolateral perspective view of a drill guide accordingto the present invention;

FIG. 65 is an anterolateral perspective view of the drill guide of FIG.64 inserted over the trial spacer assembly;

FIG. 66 is an anterior view of the trial spacer and drill guide of FIG.65;

FIG. 67 is an anterolateral perspective view of the trial spacer anddrill guide of FIG. 65 with a drill;

FIG. 68 is an anterolateral perspective view of the trial spacer of FIG.67 after the grooves have been drilled and the drill guide is removed;

FIG. 69 is an anterolateral perspective view of the trial spacer of FIG.68 with the cam cutter guide slid over the shaft and a cam cutter priorto cutting cams into the vertebrae;

FIG. 70 is a perspective view of the cam cutter of FIG. 69;

FIG. 71 is an anterolateral perspective view of the intervertebral spaceafter the grooves and cams have been cut by the drill and the camcutter;

FIG. 72 is an anterolateral perspective view of an artificial discimplant according to the present invention including a securingmechanism in the form of three cam shafts with deployable cam lobemembers;

FIG. 73 is an enlarged anterolateral perspective view of the artificialdisc implant of FIG. 72 with one cam shaft removed to show the retainermembers;

FIG. 74 is lateral view of the implant of FIG. 72 as implanted in theintervertebral space;

FIG. 75 is an anterolateral perspective view of the implant of FIG. 72with cam members with sharpened edges for cutting into bone whendeployed into the vertebra;

FIG. 76 is an anterolateral perspective view of the implant of FIG. 75with the cam members fully deployed;

FIG. 77 is an anterior perspective view of a trial spacer memberaccording to the present invention inserted into the intervertebralspace;

FIG. 78 is an anterolateral perspective view of a trial spacer member ofFIG. 77 with a drill guide inserted over the trial spacer for drillingoffset grooves into the vertebrae for installing cam shafts directlyinto the vertebrae;

FIG. 79 is an anterolateral perspective view of a trial spacer member ofFIG. 77 with the cam shafts inserted into the trial spacer for beingimbedded in the vertebra prior to insertion of the implant;

FIG. 80 is an anterolateral perspective view of a trial spacer of FIG.79 with the cam shafts imbedded into the offset grooves in thevertebrae;

FIGS. 81-84 show a sequence from a posterior viewpoint detailing theoperation of the cam shafts from an initial resting point on the trialspacer in FIG. 81 to being cammed up into the vertebrae in FIGS. 82 and83, and being imbedded into the vertebrae in FIG. 84 so that the trialspacer may be removed and the implant may be inserted;

FIG. 85 is an anterolateral perspective view of an artificial discimplant according to the present invention with one cam shaft hidden,wherein the cam shafts are first imbedded into the vertebrae before theimplant is inserted;

FIG. 86 is an anterior view of the artificial disc implant of FIG. 85wherein the cam shafts have been rotated 90 degrees to secure theimplant with respect to the vertebrae;

FIG. 87 is a posterolateral view of the trial spacer of FIG. 79 with thecam shaft driver driving one of the cam shafts up into the uppervertebrae, which is hidden for illustration purposes;

FIG. 88 is a side perspective view of the trial spacer system comprisedof a trial spacer assembly, a drill set, and a trial spacer insertertool;

FIG. 89 is a posterolateral perspective view of the trial spacerassembly of FIG. 88;

FIG. 90 is an anterolateral perspective view of the trial spacerassembly of FIG. 88;

FIG. 91 is an enlarged longitudinal cross-sectional view of the trialspacer assembly of FIG. 88 with the gripping mechanism of the insertertool inserted therein;

FIG. 92 is a side perspective view of the inserter tool of FIG. 88;

FIG. 93 is an exploded view of the inserter tool of FIG. 88;

FIG. 94 is a longitudinal cross-sectional view of the inserter tool andtrial spacer assembly of FIG. 88;

FIG. 95 is an anterolateral perspective view of an artificial discimplant according to the present invention with the securing mechanismsfully deployed;

FIG. 96 is a posterolateral perspective view of a cam shaft securingmechanism according to the present invention illustrating a cammingsurface;

FIG. 97 is an anterolateral perspective view of the cam shaft of FIG. 96with the head hidden disposed in a test block mimicking a securingmechanism for an implant for illustration of the operation of the camshaft. The cam shaft is shown in an undeployed position, a partiallydeployed position, and fully deployed, from left to right;

FIG. 98 is a posterolateral perspective view of a cam shaft securingmechanism according to the present invention illustrating a flat cammingsurface;

FIG. 99 is an anterolateral perspective view of the cam shaft of FIG. 98with the head hidden disposed in a test block mimicking a securingmechanism for an implant for illustration of the operation of the camshaft. The cam shaft is shown in an undeployed position, a partiallydeployed position, and fully deployed, from left to right;

FIG. 100 is a posterolateral perspective view of a cam shaft securingmechanism according to the present invention illustrating a dualchamfered camming surface;

FIG. 101 is an anterolateral exploded view of the artificial discimplant of FIG. 95;

FIG. 102 is an anterolateral perspective view of an alternate embodimentof a cam shaft securing mechanism according to the present invention;

FIG. 103 is a side view of an alternate embodiment of a cam shaftsecuring mechanism according to the present invention illustratingcupped cam members;

FIG. 104 is a side view of an alternate embodiment of a cam shaftsecuring mechanism according to the present invention illustratingcontoured cam members;

FIG. 105 is a top view of an alternate embodiment of a cam shaftsecuring mechanism according to the present invention illustratingcontoured cam members;

FIG. 106 is an anterolateral perspective view of an alternate embodimentof the artificial disc implant according to the present invention;

FIG. 107 is an inverted anterolateral exploded view of the artificialdisc implant of FIG. 95;

FIG. 108 is a perspective view of the implant inserter tool andartificial disc implant according to the present invention;

FIG. 109 is an exploded view of the implant inserter tool of FIG. 108;

FIG. 110 is an enlarged perspective view of the implant and implantinserter tool of FIG. 108 with the upper disc member and upper housingmember of the tool hidden for illustration purposes;

FIG. 111A is an enlarged perspective view of the implant and implantinserter tool of FIG. 108 illustrating the engagement of the implant andinserter tool;

FIG. 111B is an enlarged perspective view of the underside of theimplant and implant inserter tool of FIG. 108 illustrating theengagement of the implant and inserter tool;

FIG. 112A is a side view of the implant inserter tool of FIG. 108illustrating the initial disengaged position of the inserter tool;

FIG. 112B is an enlarged side view of the gripping mechanism of theinserter tool of FIG. 108 illustrating the position of the grippingmechanism in the initial disengaged position;

FIG. 113A is a side view of the implant inserter tool of FIG. 108illustrating the engaged position of the inserter tool;

FIG. 113B is an enlarged side view of the gripping mechanism of theinserter tool of FIG. 108 illustrating the gripping mechanism in theengaged position.

FIG. 114 is a anterolateral perspective view of a bearing member of anintervertebral implant according to the present invention illustrating adeployable securing member in a bone engaging orientation;

FIG. 115 is an exploded anterolateral perspective view of the bearingmember of FIG. 114;

FIG. 116 is an anterior view of the bearing member of FIG. 114illustrating the deployable securing member in an undeployedconfiguration, wherein the securing member is completely submergedwithin the bearing member so as to not protrude above the upper bearingsurface;

FIG. 117 is an anterior view of the bearing member of FIG. 116illustrating the deployable securing member in a deployed configuration,wherein the securing member protrudes above the upper bearing surfacefor engagement with a bone;

FIG. 118 is a plan view of the bearing member of FIG. 114 illustratingthe deployable securing member in a deployed configuration;

FIG. 119 is a lateral cross-sectional side view of the bearing member ofFIG. 114, illustrating the deployable securing member receiving portion,and the securing member in a deployed configuration;

FIG. 120 is a bottom view of the bearing member of FIG. 114,illustrating the concave articulation surface disposed on an innersurface of the bearing member;

FIG. 121 is a posterior view of the bearing member of FIG. 114,illustrating the deployable securing member in a deployed configurationand a centrally located marking member disposed in the bearing memberbody;

FIG. 122 is a partially exploded anterolateral perspective view of analternate embodiment of an intervertebral implant according to thepresent invention illustrating a plurality of securing members of thesecuring member, an elongate actuating member, and a pair of prongs usedfor inserting the implant into the intervertebral space;

FIG. 123 is an exploded anterolateral perspective view of theintervertebral implant of FIG. 122;

FIG. 124 is an exploded posterolateral perspective view of theintervertebral implant of FIG. 122;

FIG. 125 is an anterolateral perspective view of the intervertebralimplant of FIG. 122 illustrating the prongs secured to the upper bearingmember for manipulation of the implant and the elongate actuating memberpositioned remotely from the deployable securing member prior toinsertion thereof;

FIG. 126 is an anterolateral perspective view of the intervertebralimplant of FIG. 122 showing the deployable securing member in a deployedorientation with the elongate actuating member inserted into the implantbody;

FIG. 127 is an partially exploded anterolateral perspective view of analternate embodiment of an intervertebral implant with a securing memberaccording to the present invention illustrating a plurality of securingmembers, an elongate actuating member, and a pair of prongs used forinserting the implant into the intervertebral space;

FIG. 128 is an anterolateral perspective view of the implant of FIG. 126illustrating the plurality of securing members in an undeployedconfiguration prior to insertion of the actuating member;

FIG. 129 is an anterolateral perspective view of the intervertebralimplant of FIG. 127 showing the deployable securing member in a deployedconfiguration with the elongate actuating member inserted into theimplant body;

FIG. 130 is a posterolateral perspective view of the implant of FIG.127;

FIG. 131 is a partially exploded anterolateral perspective view of analternate embodiment of an intervertebral implant with a securing memberaccording to the present invention illustrating the securing member in adeployed and an undeployed configuration, a securing member inserter,and a pair of prongs used for inserting the implant into theintervertebral space;

FIG. 132 is an anterolateral perspective view of the intervertebralimplant of FIG. 131 illustrating the securing member disposed within thesecuring member inserter;

FIG. 133 is an anterolateral perspective view of the implant of FIG. 131illustrating the securing member in a deployed configuration; and

FIG. 134 is a lateral cross-section along an anterior-posterior axis ofthe implant of FIG. 131 illustrating the securing member in a deployedconfiguration.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In a preferred embodiment, such as illustrated in FIGS. 1-4, anartificial disc device 001 comprises an upper shell 100 and lower shell110. The upper shell 100 comprises a substantially concave recessportion 120, and the lower shell 110 comprises a substantially convexportion 130. Although not preferred, the concave and convex portions maybe switched such that the upper shell 100 may alternatively comprise theconvex portion 130.

The convex portion 130 comprises a convex articulation surface 131, andthe concave portion 120 comprises a concave articulation surface 121. Itis preferred that the articulation surfaces 121 and 131 havesubstantially matching geometries or radiuses of curvature although somemismatch of curvature may be desired to provide a combination of rollingand sliding motion to occur between the articulation surfaces 120 and121. The geometries may be complex in nature but preferably are ball andsocket style. The convex portion 130 and concave portion 120 may extendsubstantially to the outer perimeter of the shell 100, 110 asillustrated in FIG. 4, or may be formed, typically with a smaller radiusof curvature inward a predetermined distance from the outer perimeter ofthe shell 100, 110. Each shell 100, 110 is preferably manufactured fromPEEK or fiber reinforced PEEK or other biocompatible polymer combinationor radiolucent material demonstrating very low surface wear in highrepetition wear testing.

The artificial disc device 001 preferably comprises one or morerestraint portion(s) 220 or structure located on one or both of theshell members 100, 110 to help prevent the shells 100, 110 from becomingdislodged or migrating across the boney endplate 141 of the vertebrae143 after insertion. For example, the restraining portion 220 may belocated on one of the shells 100, 110 on the endplate facing surface 142in the form of directional teeth 140.

It is preferred that the footprint of the artificial disc device 001 besimilar to the footprint of the endplate although generally smaller tofit within the intervertebral space. The endplate facing surfaces 142are preferably contoured to match the contour of the endplates 141. Forexample, if the surgeon prepares the endplates to be flat, it ispreferred that the endplate facing surfaces 142 are also flat. Likewise,if the endplates 141 are prepared to be concave, it is preferred thatthe endplate facing surfaces 142 are similarly convex. It should benoted that endplates 141 that are concave will generally retain theartificial disc device 001 better since the device 001 becomes cuppedbetween the vertebrae.

Additional restraining features may be needed to assist holding theartificial disc device 001 in the predetermined position. Described inthis application are various securing mechanisms, coatings, or surfacepreparations that can be used on the endplate facing surfaces 142 torestrain an implant.

An additional embodiment of a restraint is illustrated in the artificialdisc device 001 shown in FIG. 5. In this embodiment, the surgeon maychoose to form a recess 002 in the anterior edge of the facing upper andlower vertebrae to accommodate the restraint boss 200. The restraintboss 200 is preferably an extended wall or lip from the endplate facingsurface 142 and is of a thickness suitable to block further posteriormotion. If the recess 002 is suitably formed into a pocket, therestraint boss 200 will also assist in unwanted lateral motion of theshell 100 or 110. Alternatively, the restraint boss may sit on theanterior bone surface of the vertebral body without the recess 002. Therestraint boss 200 may be included on one or both of the shells 100,110.

Upon insertion of the artificial disc device 001, the restraint boss 200acts as a stop to the shell 100, 110 as it is guided to thepredetermined position. The boss 200 also assures the device is unableto migrate posteriorly towards the spinal cord and cause injury. It ispreferred the recess 002 is generally the thickness of the boss 200 suchthat the boss 200 may be generally flush with the anterior surface ofthe vertebral body 144.

The shell 100, 110 preferably includes an attachment portion 210 whichmay be in the form of a boss, hole, post, recess, ridge, flange or otherstructure for securing of an implant insertion or removal instrument toassist with inserting or removing the implant from the intervertebralspace. For example, in the embodiment in FIG. 6A, the attachment portion210 comprises a window 211 for insertion of the head of an insertion orremoval instrument and connection holes 212 for occupation by deployablepins on each end of the window 211 situated in the instrument.

As described earlier, the restraint portion 220 on the endplate facingsurfaces 142 may be in the form of directional teeth 140 which areangled like saw teeth to encourage eased insertion across the boneyendplate 141 and resist anterior migration to help retain the shellmembers 100, 110 in the predetermined location between theintervertebral bodies. The actual form of the restraint portion 220,i.e. directional teeth 140 or a surface coating, may be found on one orboth shell 100, 110 members. The restraint portion 220 may includedifferent forms of restraint on each shell 100, 110. In addition, morethan one form of restraint may be used on each restraining portion 220.For example, the shell 100 may include a restraint portion 220 whichcomprises both directional teeth 140 with an osteo-conductive surfacecoating such as hydroxyapatite.

The shell 100, 110 may include apertures for the placement of fastenerssuch as bone screws to secure the shell 100, 110 to the endplate 141after insertion. It is preferable that the fasteners are alsomanufactured from a radiolucent material such as PEEK, however thesurgeon may choose to use fasters made of a biocompatible metal such asfrom the family of titaniums or stainless steels. It is preferable thatthese apertures are counter bored when possible to reduce the profile ofthe screw head outside the periphery of the shell 100, 110. If thedevice is equipped with a restraint boss 200, the anterior facingsurface of this boss is a preferred location for these apertures 520wherein the apertures 520 are preferably directed towards the center ofthe vertebral body.

In some forms, the restraint boss 200 may be offset to the left or theright as illustrated in FIG. 16. In this fashion, the artificial discdevice 001 can be utilized at multiple adjacent vertebral levels withoutinterference of an adjacent restraint boss 200. Similarly, the restraintboss 200 may be contoured to accommodate an adjacent restraint boss 200through a boss recess 240. Again, this orientation provides utilizationof the artificial disc device at multiple adjacent vertebral levelswithout interference of an adjacent restraint boss 200. FIG. 18 furtherillustrates this embodiment.

In other forms, the restraint boss 200 may not be integral to the shell100, 110. Instead the boss 200 may be configured as a small plate,fastened to the anterior surface of the vertebral body and extendingjust past the endplate to block back-out of the shell 100, 110 andlateral movement of the shell 100, 110 if the boss 200 is so equippedwith interlocking geometry. Further, the disc device may be blocked frombacking out by a broad flexible mesh, preferably made of a polymer suchas PEEK, fastened from the anterior surface of one vertebral body to theother.

In an alternative embodiment, the artificial disc device 001 shown inFIG. 8 comprises a restraint portion 220 in the form of a deployablepaddle 300. The paddle 300 is housed within one of the shell members100, 110 as illustrated in FIG. 9. The paddle 300 may be manufacturedfrom an array of biocompatible materials including but not limited topolymers such as PEEK or metals such as titanium or stainless steelalloys although radiolucent materials are preferred. In a preferredorientation, the paddle 300 is secured within the body of a shell 100,110 by a paddle restraint 310 in this case in the form of a snap joint.The paddle comprises a restraint arm 330 that may be deployed into theendplate 141 of the vertebrae 143 upon rotation of the drive head 320with the proper instrument. The restraint arm 330 may include asharpened edge if so desired. The neck portion 340 of the paddle 300 isheld by the paddle restraint 310 and is preferably configured with aprofile suitable for rotation. The restraint arm 330 may includeapertures or slots to encourage bone growth through the restraint arm330.

The endplate facing surface 142 comprises a restraint recess 350 toaccommodate the paddle 300 and the restraint arm 330 during implantinsertion. Once the disc device 001 is inserted, the restraint arm 330may be deployed into the endplate to secure the device 001 in thedesired location between the vertebrae. Several of the disclosedembodiments may require the surgeon to prepare the vertebral body 144 toaccept restraint portions 220 that are intended to become integratedinto the bone. In most cases, this preparation involves removing boneand creating restraint access 420 typically in the form of a recess,channel, slot or profile similar to the restraint feature. Obviously,the size of the restraint portion 220 will affect the size of therestraint access 420. Therefore it is beneficial that restraint portions220 that interfere with the bone are suitably sized to prevent anoversized restraint access 420 that compromises the vertebrae 143 andrisks vertebrae 143 fracture. It is preferable that both the restraintaccess 420 and restraint portion 220 have radiused edges to reducestress concentrations in the vertebral body.

In another alternative embodiment, such as shown in FIG. 13, anartificial disc device 001 comprises a restraint portion 220 in the formof an integrated fin 400 extending from the endplate facing surface 142.The fin 400 may vary in thickness and length as needed to assist inrestraining the artificial disc device 001 in a predeterminedintervertebral position. The fin 400 may include bone growth apertures410, slots, or other structure to facilitate bone growth through the finand thereby provide additional restraint to the device. Again, therestraint portion 220 may be found on one or both of the shells 100,110. Alternatively, although the implant is typically inserted from ananterior to posterior approach, the fin 400 may not necessarily beoriented in this same direction. For example, the fin 400 in FIG. 13Aillustrates a fin 400 that extends laterally across the endplate facingsurface 142. In this embodiment, a restraint access 420 is also cutlaterally across the endplate 141. There is no entry into the restraintaccess 420 from the peripheral edge of the vertebral body. Therefore,the surgeon may choose to first distract or over stretch theintervertebral space, making room for the addition height of the fin 400until the fin 400 can fall into the restraint access 420 to secure theimplant in the predetermined position. The fin 400 may be equipped witha ramped lead-in wherein the lead-in can be utilized to help distractthe vertebrae.

In an alternative embodiment, the artificial disc device 001 asillustrated in FIG. 14 may comprise a restraint portion 220 in the formof a fin 400 which accommodates a bone fastener 510 therein. It ispreferable that the bone fastener 510 is in the form of a bone screw andis manufactured from a radiolucent material such as PEEK, however thesurgeon may choose to use bone fasteners 510 made of a biocompatiblemetal such as from the family of titaniums or stainless steels. It ispreferable that the fastener aperture 520 is counter bored when possibleto reduce the profile of the screw head outside the periphery of theshell 100, 110. The fastener aperture 520 may include fastener restraintsuch as an interference spring to prevent fastener 510 back-out. Forexample, the fastener aperture 520 may have a groove inscribed thereinto house a spring that expands out of the way of the fastener 510 whiledriving the fastener and closes over the head of the fastener once thehead passes the spring.

An additional alternative embodiment of the artificial disc device 001is illustrated in FIGS. 19-21 and comprises a restraint portion 220 inthe form of a fin 400 wherein the fin 400 comprises one or moredeflectable wall portions 600. The fin 400 again comprises a fasteneraperture 520 to house an expansion fastener 610. In the preferred form,the expansion fastener 610 comprises a threaded shaft 630, to drive thefastener 610 down the aperture 520 when rotated, and an expansion shaft640 to drive apart the deflectable wall portions 600 as the fastener 610is driven forward. The aperture 520 in this configuration preferablycomprises threads 620 to complement the threaded shaft 630. As theexpansion fastener 610 is driven and causes the wall portion 600 todeflect outward a predetermined amount, these wall portions 600 willinterfere within the restraint access 420 securely holding the discdevice 001 in position. Deflection cuts 650 facilitate the deflection ofthe wall portion 600 with respect to the fastener block 660. Thedeflection cuts 650 may be orientated in different directions wherein,for example, the wall portion may deflect laterally along a verticalplane or laterally along a horizontal plane. Since the disc device 001will typically be inserted from a generally anterior surgical approach,it is preferred that the fin 400 also be orientated generally anteriorto posterior.

Another embodiment of an artificial disc device 001 is illustrated inFIGS. 22-24 and comprises a restraint portion 220 in the form of a fin400. The fin 400 in this embodiment is preferably laterally offset toone side or the other. The fin 400 preferably comprises an interferenceportion 710, typically in the form of a threaded or unthreaded hole orrecess. After the shell 100, 110 having this feature is inserted intothe predetermined position, an alignment instrument (not shown),comprising a drill guide orientated to the implant may be utilized tocreate a pilot hole 720 through the vertebrae that is directed at theinterference portion 710. A bone fastener 510, preferably in the form ofa bone screw, is then driven into the pilot hole 720, and in interferingrelation with the interference portion 710, secures the disc device 001in a predetermined position. The fastener 510 in this embodiment ispreferably threaded where it contacts the bone, and may interfere withthe fin 400 by threading through it, extending through it, abutting it,or any other interference method. In embodiments wherein a fastener 510is threaded or otherwise engaged into a deformable implant material,(i.e. an implant manufactured from PEEK), the material itself may serveas adequate protection against fastener 510 back-out.

In an alternative embodiment, a shell 100, 110 is illustrated in FIG. 25comprising a restraint portion 220 in the form of a deflectable stop800. The deflectable stop 800 is preferably integrated into the endplatefacing surface 142 adjacent the posterior end of the shell 100, 110. Inthe undeflected orientation and from this point of integration, thedeflectable stop 800 gradually extends anterior and away from theendplate facing surface 142. As the shell 100, 110 is inserted betweenthe vertebrae, the deflectable stop 800 may deflect into the stop recess810 as the shell passes over the complementary profiled restraint access420 created by the surgeon as illustrated in FIG. 26. Once the shell100, 110 is positioned in its predetermined location, the deflectablestop 800, and the restraint access 420 are aligned such that the stop800 will spring back into the restraint access 420 securely retainingthe shell 100, 110 in position.

Similarly, and in a further alternative embodiment, an artificial discdevice 001 is illustrated primarily in FIGS. 27-29 comprising arestraint portion in the form of a deflectable capture 900 preferablyintegrated into the endplate facing surface 142 adjacent the posteriorend of the shell 100, 110. An interlock key 910, comprising a bone boss930 and a connection pod 940 with interlock structure complementary tothe interlock key 910, is situated in a preformed restraint access 420such as shown in FIG. 30. As the shell 100, 110 is inserted across thevertebral endplate 141, the deflection arms 960 are pushed open by theconnection pod 940 until the pod 940 is seated in the pod canal 950 andthe deflection arms 960 are able to spring back into a pod 940 lockingposition. The pod canal 950 may include complementary structure, such asa tongue and groove arrangement 920, to secure the pod 940 to the shell100, 110.

Another alternative embodiment is illustrated in FIG. 31 wherein anartificial disc device 001 comprises a restraint portion 220 in the formof a fixed fin 400, and an insertable locking fin 1000. Restraint access420 is formed in the vertebral endplate 141 complementing the positionof the fixed fin 400 and the locking fin 1000 on the shell 100, 110 asillustrated in FIG. 33. The shell 100, 110 is inserted, with the lockingfin 1000 removed, to its predetermined position between theintervertebral endplates. The locking fin 1000 preferably comprises afriction fit interlocking architecture such as tongue and groove withthe shell 100, 110 to secure the locking fin to the shell 100, 110 andrestrict back-out. The locking fin 1000 and the fixed fin 400 areorientated non-parallel to each other such that once the locking fin1000 is inserted, the corresponding shell is restrained to the desiredposition on the endplate 141.

The artificial disc device 001 can take a form of a non-constrainedarticulating joint wherein the device 001 has no built in features tolimit motion between the articulation surfaces 121 and 131. In somecases, this can be problematic if the anatomy of the user, by hard orsoft tissue, does not perform this function since it is possible that ashell 100, 110 can dislocate off the other shell 100, 110 andpotentially become jammed. In addition, excessive unnatural motion atthe device 001 may cause injury to the user. For these reasons it may beadvantageous to limit the motion occurring between the articulationsurfaces 121 and 131.

The artificial disc device may include a motion-limiting portion. In theshell 110 embodiment shown in FIG. 36, this motion-limiting portion isin the form of a motion-limiting stop 1100 that is a protruding surfacediscontinuous with the curvature of the convex articulating surface 131.Alternately, the stop may instead be formed on the shell 100, or on bothshells 100, 110. As one shell articulates against the other, the stopwill limit the freedom of motion that can occur.

The motion limit portion may take numerous forms. For example, one ofthe shells 100, 110 may comprise a limiter holder 1120 to house a limitpost 1130. Alternatively the limit post 1130 may be integrated into thearticulating surface of the shell 100, 110. The limit post 1130 extendsinto a limit recess 1110 preferably bound by a limit wall 1140. As theshells 100, 110 articulate against each other, interference between thelimit post 1130 and the limit wall 1140 limit the motion that can occurbetween the shells 100 and 110. Clearly, by adjusting the shape and/orsize of the limit recess 1110, motion can be limited in varying amountsin different directions. For example, motion can be limited to 10degrees of flexion but only 5 degrees of lateral bending at the joint.

The artificial disc device 001 may be configured for use when all or aportion of the vertebral body 144 is removed such as in a corpectomysurgery. As seen in FIGS. 37 and 38, the majority of a vertebral body144 is removed and replaced with a vertebral strut 1200. The strut 1200comprises any combination of convex articulation surfaces 131 and/orconcave articulation surfaces 121. In addition, the body of the strut1200 preferably comprises fastener apertures 520 to house bone fasteners510 (not shown) secured into the remaining bone 1210 of the vertebrae143 securing the vertebral strut 1200 in the predetermined position.Complementary shells 100, 110 articulate with the vertebral strut 1200.The vertebral strut may also comprise apertures for boney ingrowth orother osteo-conductive coatings or surfaces.

FIG. 41 shows an artificial disc implant 1310 having an upper componentor member 1312 and a lower component or member 1314 with the members1312 and 1314 having a bearing interface 1316 therebetween that allowsthe members 1312 and 1314 to shift or articulate relative to each otherwhen implanted and secured in an intervertebral space. The bearinginterface 1316 can be in the form of a concave recess 1318 formed in theinner or lower surface 1320 of the upper disc member 1312 (FIG. 42), anda convex dome 1322 that projects up from inner or upper surface 1324 ofthe lower disc member 1314 (FIG. 43). Manifestly, the orientation of thebearing interface 1316, and specifically the concave recess 18 andconvex dome 1322 can be reversed such that the recess 18 would be formedon the lower implant member 1314 while the dome 1322 would be formed onthe upper member 1312. Preferably, the radius of curvature of theconcave recess 1318 and convex dome 1322 are the same for smooth slidingengagement therebetween, although differences in the radius of curvaturecan also be utilized if desired.

Preferably, both the upper and lower disc members 1312 and 1314 areformed of a PEEK (polyetheretherketone) material which has been found toprovide the disc implant 1310 with excellent strength and wearcharacteristics that are desirable for a joint that is intended formotion preservation such as the artificial disc implants describedherein.

Referring to FIG. 44, a trial spacer assembly 1326 is shown thatincludes a forward, trial spacer portion 1328 that is inserted into theintervertebral space 1330 between adjacent, upper and lower vertebralbodies 1332 and 1334. The trial spacer portion 1328 has a generallytongue-shaped configuration including a rounded distal end 1336 andgenerally flat upper and lower surfaces 1338 and 1340, as best seen inFIGS. 45 and 46. The outer surfaces of the trial spacer portion 1328present a generally smooth, continuous periphery of the trial spacerportion 1328 for smooth insertion thereof into the intervertebral space1330. This smooth tongue configuration for the trial spacer portion 1328substantially corresponds to the peripheral configuration of the discimplant 1310 less the integrated securing mechanism thereof, as will bedescribed hereinafter.

The forward trial spacer portion 1328 is connected to an enlarged rearportion 1342 that remains outside the intervertebral space 1330 afterthe trial spacer portion 1328 is fully inserted therein, as shown inFIG. 44. The trial spacer portion 1328 and rear portion 1342 have ahollow interior with the rear portion 1342 having a generallyrectangular box-like configuration. As shown, there is a transverseshoulder surface 1343 between the trial spacer portion 1328 and rearportion 1342 that acts as a stop to engage the vertebral bodies 1332 and1334 with the trial spacer portion 1328 fully inserted into theintervertebral space 1330.

The hollow portion of the tongue 1328 contains a pair of plates 1344 and1346 with the upper plate 1344 including several upstanding posts 1348and the lower plate 1346 including several depending posts 1350corresponding in positioning to the posts 1348, as can be seen in FIGS.47-49. The posts 1348 and 1350 are used to form correspondingly spacedopenings in the facing surfaces of the vertebral bodies 1332 and 1334.As shown, the posts 1348 and 1350 have blunt end surfaces, althoughother configurations for these ends can also be used to ease driving ofthe posts 1348 and 1350 into the bone surfaces.

Referring to FIG. 47, the upper plate 1344 includes raised side platformportions 1352 each having three posts 1348 equally spaced therealong andupstanding therefrom. A central ramp portion 1354 is recessed from theraised side portions 1352 at its rear end and extends at an inclineupwardly and forwardly toward the forward end 1382 of the upper plate1344. Intermediate vertical wall portions 1356 extend along either sideof the ramp portion 1354 to interconnect the ramp portion 1354 and theside platform portions 1352 of the upper plate 1344. The lower plate 46has a similar configuration to the upper plate 1344 in that it also haslowered, side platform portions 1358 that each include three posts 1350equally spaced therealong and depending therefrom. A central rampportion 1360 extends between the side portions 1358 and is raised at itsrearward end and extends at an incline downwardly and forwardly towardthe forward end 1384 of the lower plate 1346. Intermediate vertical wallportions 1352 interconnect the side platform portions 1358 and thecentral ramp portion 1360.

The corresponding platform portions 1352 and 1358 of the plates 1344 and1346 cooperate to form a wedge-shape elongate openings or channels 1367and 1369 by way of their facing inclined surfaces 1364 and 1366. Morespecifically, the corresponding wall portions 1356 and 1362 and theinclined surfaces 1364 and 1366 cooperate to form wedge-shaped sidechannels 1367 and 1369 which are used to drive the plates 1344 and 1346apart for creating the indentations or pocket openings in the vertebralbodies, as described further hereinafter.

Referring to FIG. 48, in addition to the upper and lower plates 1344 and1346, the internal components of the trial spacer assembly 1326 includea spreader device 1368, and a generally block-shaped, closing device1370 shown in their compact or insertion/removal configuration.Referring to FIG. 50, the closing wedge device 1370 has upper and lowerprojecting arms 1372 and 1374 including inclined facing surfaces 1376and 1378, respectively. The surfaces 1376 and 1378 cooperate to form aV-shaped opening 1380. In the insertion configuration, the closingdevice 1370 has the ramp portions 1354 and 1360 of the plates 1344 and1346 fully received in the V-shaped opening 1380 with the surfaces 1376and 1378 fully engaged on the ramp portions 1354 and 1360, as shown inFIGS. 48 and 49. In this manner, the plates 1344 and 1346 are heldtogether with the respective forward ends 1382 and 1384 in engagement,as is best seen in FIG. 49.

The spreader device 1368 has an enlarged rear, box-shaped portion 1386that fits in the hollow space defined by a box-shaped portion 1342 ofthe trial spacer assembly 1326. The spreader device 1368 also includesforwardly projecting arms 1388 and 1390 laterally spaced so that thewedge device 1370 fits therebetween, as can be seen in FIGS. 48 and 49.As best seen in FIG. 48, the arms 1388 and 1390 have a wedgeconfiguration so that they fit into the corresponding wedge channels1367 and 1369 formed on either side of the plates 1344 and 1346. In thisregard, each of the wedge arms 1388 and 1390 have inclined surfaces 1392and 1394 that extend from their rear ends at the portion 1386 and taperdown toward each other at their forward ends in the channels 1367 and1369.

Accordingly, to drive the plates 1344 and 1346 apart, the spreaderdevice 1368 and wedge device 1370 are moved in opposite directions withthe wedge device 1370 being advanced forwardly so that the inclinedsurfaces 1392 and 1394 cam against the corresponding plate inclinedsurfaces 1364 and 1366 to drive the upper plate 1344 in an upwarddirection toward the vertebral body 1332 and the lower plate 1346downwardly toward the vertebral body 1334. The rear portion 1386 of thespreader device 1368 has a window opening 1396 to allow the closingdevice 1370 to fit therethrough so that as the spreader device 1368 isadvanced, the wedge device 1370 can be retracted off of the rampportions 1354 and 1360 of the plates 1344 and 1346 and through thewindow opening 1396 to allow the plates 1344 and 1346 to be spreadapart. In addition, the trial spacer portion 1328 is provided withthrough openings 1398 so that the posts 1348 and 1350 can be driventherethrough and into the facing surfaces of the vertebral bodies 1332and 1334. As can be seen in FIG. 45, openings 1398 are shown in theupper portion of the trial spacer portion 1328 through which the upperposts 1350 are driven. Similar openings are provided in the lowerportion of the trial spacer portion 1328 for the lower posts 1350.

To remove the trial spacer portion 1328 from the intervertebral space1330, the trial spacer assembly 1326 is shifted back from its spread orexpanded configuration to its insertion/removal or compact configurationwith the plates 1344 and 1346 held together with the closing device1370. For this purpose, the operation of the spreader device 1368 andthe closing device 1370 is reversed with the closing device 1370 beingadvanced forwardly through the window opening 1396 of the spreaderdevice 1368 and the spreader device 1368 being retracted rearwardlyuntil the plate ends 1382 and 1384 are brought together as shown in FIG.49 with the surfaces 1376 and 1378 of the closing device 1370 once morefully engaged on the ramp surfaces 1354 and 1360. As the trial spacerassembly 1326 is shifted back to its compact configuration, the posts1348 and 1350 are retracted back through their corresponding openings1398 in the trial spacer portion 1328 and into the hollow space therein.

After the trial spacer assembly 1326 is utilized as described above toform openings or indentations 1398 in the facing surfaces of thevertebral bodies 1332 and 1334, the implant 1310 is inserted into theintervertebral space 1330 via inserter tool 1400. The inserter tool 1400has an elongate shaft 1402 and an enlarged head 1404 at its end in whichit carries the disc implant 1310 for insertion thereof. Shaft 1402 andthe head 1404 are formed by an upper elongate tool member 1406 and alower elongate tool member 1408 having shaft portions 1410 and 1412,respectively, and an associated head portion 1414 and 1416 at theirrespective ends. The upper and lower tool members 1406 and 1408 are ableto slidingly reciprocate relative to each other for removal of the disc1310 from the intervertebral space 1330, as will be described more fullyhereinafter.

As shown in FIG. 51, the tool head 1404 has a forward opening 1318between upper and lower plate portions 1420 and 1422 of the respectiveupper and lower head portions 1414 and 1416. The opening 1418 betweenthe plate portions 1420 and 1422 is sized to receive the implant 1310therein. In this regard, each plate portion 1420 and 1422 has respectiveside slots 1424 and 1426 formed therein. The slots 1424 and 1426 allowthe securing mechanism, in the form of upstanding posts 1428 that areintegral with and project up from the upper disc member 1312, anddepending posts 1430 that are integral with and project downwardly fromthe lower disc member 1314, to fit therein. The slots 1424 and 1426 aredefined by side prongs that extend along either side of a centralprojection of each of the tool member head portions 1414 and 1416. Morespecifically, the upper head portion 1414 has side prongs 1432 on eitherside of central projection 1434, and the lower head portion 1416 hasside prongs 1436 on either side of central projection 1438. The posts1428 are formed in two rows of three equally spaced posts 1428 on eitherside of the upper disc member 1312, and the lower posts 1430 are formedsimilarly in two rows of three equally spaced lower posts 1430 on lowerdisc member 1314 so that the posts 1428 and 1430 correspond to thespacing and positioning of the posts 1348 or 1350 of the plates 1344 and1346, and the openings 1398 that they form in the vertebral bodies 1332and 1334.

As shown in FIG. 51, the implant 1310 is arranged so that the straightupper and lower ends 1438 and 1440 thereof are facing rearwardly so thatthey abut against the shoulder abutment walls 1442 and 1444 at the rearend of the disc receiving opening 1418 in the tool head 1404. In thisregard, the upper and lower actuator ends 1445 and 1447 are arrangedforwardly so as to be at the trailing end of the disc implant 1310 as itis inserted into the tool head opening 1418. So that the upper plates1420 and 1422 substantially match the configuration of the upper andlower disc members 1312 and 1314, the prongs 1432 and 1436 do not extendas far forwardly as the adjacent central projection 1434 and 1438,respectively. In addition, the peripheral edges of the side prongs 1432and 1436 and the respective central projections 1434 and 1438 have anactuate chamfer to match that of the ends 1445 and 1447 of the discmembers 1312 and 1314, respectively. In this manner, with the disc 1310fully received in the tool head opening 1418 as shown in FIG. 52, theprojecting ends 1445 and 1447 of the disc implant 1310 present asubstantially smooth, continuous surface in combination with thecorresponding, adjacent edges of the prongs 1432 and 1436 and centralprojections 1434 and 1438.

Referring to FIG. 52, the implant posts 1428 and 1430 are received inthe respective slots 1424 and 1426. As shown, the rearmost posts 1428abut against the end of the slots 1424 with the upper and lower discmember ends 1439 and 1440 engaged against the shoulder walls 1442 and1444 with the disc implant 1310 fully received in the tool head opening1418. Similarly, the rearmost lower posts 1430 are engaged at the end oflower slots 1426 with the upper and lower disc ends 1439 and 1440engaged against the shoulder walls 1442 and 1444 with the disc implant1310 fully received in the tool head opening 1418. As shown, the spacingthe plates 1420 and 1422 is such that with the posts 1428 and 1430received in the slots 1424 and 1426, the upper ends of the posts 1428and 1430 will be substantially flush with the top and bottom surfaces1446 and 1448 of the plate portion 1420 and 1422, respectively. In thismanner, the disc implant 1310 is smoothly inserted into theintervertebral space 1330 with the inserter tool 1400. Also, theinserter tool plates 1420 and 1422 are spaced so as to distract thevertebral bodies 1332 and 1334 apart for fitting the disc implant 1310therebetween. In other words, the spacing between the surfaces 1446 and1448 of the respective plates 1420 and 1422 is slightly greater than thespacing between the surfaces 1338 and 1340 of the trial spacer portion1328 of the trial spacer assembly 1326. This allows the disc posts 1428and 1430 to be fit into the openings 1398.

More specifically, the upper and lower tool members 1406 and 1408preferably include respective, laterally extending stop members 1450 and1452 that are spaced slightly rearwardly of the rear ends of the slots1424 an 1426. The tool 1400 is advanced forwardly to fit the tool head1404 and artificial disc 1310 carried thereby into the intervertebralspace 1330. The tool 1404 continues to be advanced forwardly until thestops 1450 and 1452 abut against the vertebral bodies 1332 and 1334 toprovide the user an indication that the tool head 1404 and theartificial disc 1310 carried thereby are fully received in theintervertebral space 1330. With the stops 1450 and 1452 engaged againstthe respective vertebral bodies 1332 and 1334, the posts 1428 and 1430are now properly aligned with the pocket openings 1398 formed in each ofthe vertebral bodies 1332 and 1334.

As previously mentioned, the tool members 1406 and 1408 are slidablerelative to each other so that one of the members 1406 and 1408 can beretracted while the other member 1406 or 1408 remains in its advancedposition with the corresponding stop 1450 or 1452 engaged against thecorresponding vertebral body 1332 or 1334. As shown in FIG. 54, uppertool member 1406 is retracted while the lower tool member 1408 remainsin its advanced position with the stop 1452 thereof engaged against thevertebral body 1334. With the plate 1420 retracted out from theintervertebral space 1330, the distracted vertebral body 1332 will shiftdown toward the vertebral body 1334 causing the posts 1428 of the discupper member 1312 to be received in the corresponding preformed pocketopenings 1398 in the vertebral body 1332. Thereafter, the lower toolmember 1408 is retracted to pull the plate member 1422 out from theintervertebral space 1330 so that the posts 1430 can fall into thecorresponding preformed pocket openings 1398 formed in the vertebralbody 1334, as shown in FIG. 55. With the disc implant 1310 secured tothe vertebral bodies 1332 and 1334 in the intervertebral space 1330therebetween via the fitting of the posts 1428 and 1430 into the pocketopenings 1398, the risk that the disc 1310 will be extruded out from theintervertebral space 1330 is substantially minimized as the vertebralbodies 1332 and 1334 move relative to each other via the bearinginterface 16 between the secured upper and lower disc members 1312 and1314.

In the next trial spacer and disc implantation and securing system, atrial spacer assembly 1450 as shown in FIG. 56 is employed. The trialspacer assembly 1450 also is utilized to form features in the vertebralbodies 1334 and 1336 for receipt of the securing mechanism that isassociated with the artificial disc implant 1452 (FIG. 52). The discimplant 1452 only varies from the disc implant 1310 in the securingmechanism employed so that the common features between the disc implants1310 and 1452 will not be described in detail hereinafter.

The trial spacer assembly 1450 has a forward, trial spacer portion 1454that has an outer, peripheral configuration substantially matching thatof the disc implant 1452 less the securing mechanism thereof. The trialspacer assembly 1450 also includes a rearwardly extending shaft portion1456. The trial spacer assembly 1450 is formed from two components. Asshown in FIG. 58, the main trial spacer member 1458 includes a headtrial spacer portion 1460 and a rearwardly extending shaft portion 1462.The shaft portion 1458 has an elongate lower groove 1464 formed alongits entire length, and the head portion 1460 also includes an elongatelower groove 1466 aligned with the shaft groove 1464, as shown in FIG.58. In addition, the head portion 1460 has a pair of upper grooves 1468and 1470 on either side thereof. The grooves 1464-1470 are used to formfeatures in the vertebral bodies 1332 and 1334 for receipt of thesecuring mechanism of the disc implant 1452, as described more fullyhereinafter.

The second component of the trial spacer assembly 1450 is a head coverand handle member 1472. The member 1472 includes a head cover portion1474 that consists of a laterally extending, rear flange portion 1474from which a central lower prong 1476 and a pair of upper prongs 1478extend forwardly. Shaft handle portion 1480 extends rearwardly from theflange portion 1474 and has a hollow throughbore 1482 extendingtherethrough opening to the flange portion 1474, as seen in FIGS. 60 and61.

The trial spacer assembly 1450 is assembled by sliding the head coverand handle member 1472 over the trial spacer member 158 with the shaftportion 1462 fitting into the throughbore 1482 and the prongs 1476 and1478 fitting into the corresponding grooves 1466-1470 of the trialspacer head portion 1460. Referring to FIG. 56, the throughbore 1482 hasa generally D-shaped configuration so that the shaft portion 1462 isnon-rotatably received therein. Further, as can be seen in FIG. 57, theprongs 1476 and 1478 fit into the corresponding grooves 1466-1470 suchthat the outer, peripheral surface of the trial spacer portion 1454 hasno sharp or discontinuous surfaces that might otherwise gouge thevertebral bodies 1332 and 1334 during insertion of the trial spacerportion 1454 into the intervertebral space 1330. Also, the trial spacerportion 1460 is provided with three laterally extending stop membersincluding central, upper stop member 1484 that extends laterally betweenthe upper grooves 1468 and 1470, and side, lower stop members 1486 thatextend laterally on either side of the central lower groove 1466 withall three stop members 1484 and 1486 being adjacent the rear end of thetrial spacer portion 1460.

FIG. 62 shows the trial spacer portion 1454 inserted into theintervertebral space 1330 between adjacent vertebral bodies 1332 and1334 for assessing the size of the intervertebral space 1330 so as to beable to accurately select an appropriately sized artificial disc 1452for implantation therein. As shown in FIG. 62, the trial spacer portion1454 is fully received in the intervertebral space 1330 with the stops1484 and 1486 engaged against the vertebral bodies 1332 and 1334 and theshaft portion 1462 extending outside the intervertebral space 1330 andaway therefrom. Thereafter, the head cover and handle member 1472 areslid off and removed from the trial spacer member 1458 leaving thegrooved trial spacer portion 1460 in the intervertebral space 1330 withthe shaft portion 1462 extending rearwardly therefrom, as shown in FIG.63.

At this point, the trial spacer member 1458 is used in cooperation witha drill guide 1488 for drilling grooves in the vertebral bodies 1332 and1334 at the facing surfaces thereof. Referring to FIG. 64, the drillguide 1488 has a triangular-block body 1490 with a pair of upperthroughbores 1492 extending through the body 1490, and anirregularly-shaped, enlarged central throughbore 1494 between and belowthe upper, side throughbores 1492. The enlarged, central throughbore1494 is sized so that the drill guide 1488 can be slid along the trialspacer member 1458 with the shaft portion 1462 fitting in the upperportion of the central throughbore 1494, as shown in FIG. 65. Referringnext to FIG. 66, it can be seen that the upper side throughbores 1492are aligned with the upper grooves 1468 and 1470 in the trial spacerportion 1460 to cooperate therewith in guiding a drill 1496 (FIG. 67)for cutting grooves in the upper vertebral body 1332. Similarly, thelower portion of the central throughbore 1494 of the drill guide 1488cooperates with the lower groove 1464 in the shaft portion 1462 andlower groove 1466 in the trial spacer portion 1460 to form an openingthrough which the drill bit 1496 is guided for cutting a groove in thelower vertebral body 1334. FIG. 68 shows the pair of upper grooves 1498formed along either side of the facing surface of the vertebral body1332 and the lower groove 1500 formed centrally in the facing surface ofthe lower vertebral body 1334 with the drill guide 1488 removed from theshaft portion 1462 for purposes of illustrating the grooves 1490 and1500.

Next, a cam cutter 1502 is advanced through the bores 1492 and 1494 in amanner similar to the drill bit 1496. The cam cutter 1502 has a reducedsize, radially offset cutting end 1504 including several cutting bladeportions 1506, and a counter bore cutting portion 1508 at the rearthereof. An enlarged shaft 1510 extends rearwardly from adjacent to thecounter bore cutting portion 1508. The shaft 1510 is sized to fit intothe openings through the drill guide 1488 formed in cooperation with thetrial spacer member 1458, as previously described with respect to thedrill bit 1496. FIG. 70 is a view of the cam cutter 1502 showing thebell-shaped configuration of the cutting blade portions 1506 and counterbore cutting blade portion 1508. The cam cutter 1502 is operable to cutradially enlarged recesses 1512 in the grooves 1498 and 1500 as well asenlarged counter bore portion 1514 at the rear end of the grooves 1498and 1500. Alternately, the drill bit 1496 can be provided with a steppedconfiguration to form the counter bore 1514 simultaneously with thedrilling of the grooves 1498 and 1500. Similarly, the cam cutter 1502can be avoided altogether if the securing mechanism for the artificialdisc implant 1452 is provided with cutting-type cams, as will bedescribed hereinafter.

Referring to FIG. 72, the securing mechanism of the disc implant 1452takes the form of upper cam shafts 216 secured on either side of upperdisc implant member 1518, and lower cam shaft 1520 secured centrally tothe lower disc implant member 1522. To hold the cam shafts 1516 and 1520to the respective disc members 1518 and 1522, each is provided with aplurality of spaced upwardly open, U-shaped retainer members 1524. Theretainer members 1524 have upwardly extending arms 1526 that are spacedfrom each other so that the shaft portion 1528 of the cam shafts 1516and 1520 will be received by a friction fit therebetween. In thisregard, the preferred PEEK material from which the disc members 1518 and1522 including the retainer members 1524 thereof are formed will providethe arms 1526 with sufficient strength and resiliency to provide asecure friction fit with the shaft portions 1528 snap-fit therebetweenwhile allowing for the shaft portions to be rotated to secure the discmembers 1518 and 1522 to the corresponding vertebrae 1332 and 1334.

More specifically, the cam shafts 1516 and 1522 each include several camlobe members 1530 spaced along the length thereof and a proximate discindicator member 1532 adjacent drive head 1534. Initially, the camshafts 1516 and 1520 are oriented 1480 degrees from their orientationshown in FIG. 72 for insertion of the artificial disc 1452 into theintervertebral space 1330 with the cam shafts 1516 and 1520 received inthe corresponding grooves 1498 and 1500 of the vertebral bodies 1332 and1334. In this regard, the cam lobes 1530 are rotated down into recessedslots 1536 formed in the upper surface of the upper disc member 1518.Rotating the cam shafts 1516 and 1520 via the hex drive heads 1534thereof by 1480 degrees from their insertion orientation to theirsecured orientation shifts the cam lobes 1530 into the recesses 1512 cutinto the vertebral body grooves 1498 and 1500, as shown in FIG. 74. Inthis manner, the artificial disc implant 1452 is secured in theintervertebral space 1330 against extrusion out therefrom duringarticulation of the upper and lower disc members 1518 and 1522 relativeto each other as the upper and lower vertebrae 1332 and 1334 shift viathe arcuate bearing interface formed between the members 1518 and 1522.The disc indicator member 1532 is sized to be received in the counterbore portion 1514 of the grooves 1498 and 1500. The disc member 1532 canbe provided with a pair of diametrically opposite notches 1538 about itsperiphery that cooperate with a raised nub 1540 on the disc member 1518so that the user is provided with a tactile indication that the camshafts 1516 and 1520 have been rotated by 1480 degrees from theirinsertion orientation to shift the cam lobes 1530 so that they aresubstantially fully received in the groove recesses 1512.

FIGS. 75 and 76 show alternative upper cam shafts 1542 and analternative lower cam shaft 1544. In this form, the cam members 1546have more of a flat mushroom-like configuration with sharp corner edges1548 for cutting into the vertebral bodies 1332 and 1334. In thismanner, the separate cam cutter 1502 need not be used for cutting therecesses 1512 in the vertebral body grooves 1498 and 1500. Also, it canbe seen that the drive head 1534 can have a cruciform drive recess 1550rather than having the hex drive configuration of the drive head 1534.

The next trial spacer and artificial disc implantation and securingsystem is similar to the previous system except that the securingmechanism is not associated with the artificial disc as it is insertedinto the intervertebral space 1330, but rather is first inserted intothe preformed features formed in the vertebral bodies 1332 and 1334 andthereafter deployed therefrom to interconnect the vertebral bodies andthe artificial disc implant 1552 (FIG. 85). Referring to FIG. 77, atrial spacer member 1554 is shown having upper side grooves 1556 in theforward head portion 1557 thereof and a lower central groove 1558 thatextends in the rear shaft portion 1560 thereof as well as in the forwardhead portion 1557. The cover and handle member for the trial spacermember 1554 is not shown for illustration purposes but otherwise issimilar to the previously described cover and handle member in that itis configured to ensure that the forward trial spacer portion includingthe grooved head portion 1557 can be inserted smoothly into theintervertebral space 1330 without gouging the vertebral bodies 1332 and1334.

As shown in FIG. 78, the shaft member 1560 receives a drill guide 1562thereon which has throughbores 1563 that are slightly offset from thecorresponding grooves 1556 and 1558 of the trial spacer member 1554.Accordingly, drill 1565 is guided through the bores 1563 to drillgrooves 1569 into the vertebral body 1332 that are slightly offsetupwardly from the upper grooves 1556 of the trial spacer member and agroove 1569 into the vertebral body 1334 that is slightly offsetdownwardly from the lower groove 1558 of the trial spacer member 1554.

Next, cam shafts 1567 are inserted into the intervertebral space 1330guided by the grooves 1556 and 1558 of the trial spacer member 1554, andthen they are rotated and cammed up into the offset grooves 1569 formedin the upper vertebral body 1332 and down into the offset groove 1569formed in the lower vertebral body 1334, as shown in FIGS. 79 and 80.The camming action of the cam shafts 1567 is shown in FIGS. 81-84.

In FIG. 81, a cam shaft 1567 is shown from a posterior viewpoint in itsinitial position resting in the groove 1556 of the trial spacer member1554. The head of the cam shaft is engaged by the drive tool 1570 havingan eccentric cam 1573 (FIG. 87) for camming against an anterior platformor ledge 1555 (FIGS. 77 and 79) on the trial spacer member 1554. The camshafts 1567 are cammed at both their distal shaft ends 1568 as shown inFIGS. 81-85 and 87, as well as at their proximate ends where theyinterface with drive tool 1570. In FIG. 82, the drive tool 1570 has beenrotated clockwise 90 degrees along the anterior platform 1555 of thetrial spacer member 1554. This causes the cam shaft 1567 to rotate 90degrees and the cam lobes 1572 begin to engage and imbed themselves theupper vertebra. In FIG. 83, the cam shaft 1567 is shown fully rotated180 degrees from its initial position in FIG. 81. At this point, the camlobes 1572 are embedded into the vertebra, and are held in place due tothe frictional engagement between the cam lobes 1572 and the bone.Finally, the driver 1570 may be removed, as is shown in FIG. 84. Oncethe cam shafts 1567 have been fully rotated 180 degrees, the cam lobes1572 are completely removed from the body of the trial spacer member1554. Thus, the trial spacer 1554 may be removed.

With the cam shafts 1567 rotated as shown in FIG. 84 so that the sharpcam lobes 1572 thereof are rotated up (or down) into the vertebralbodies via a cutting action generated by the cams during such rotation,the disc implant 1552 is then inserted into the intervertebral space1330. As shown in FIG. 85, the upper disc member 1564 has spiral cutouts1566 in the upper surface thereof so that rotating the cam shafts 1562again causes the cam lobes 1572 to be engaged in both the grooves of thevertebral bodies 1332 and 1334 as well as tightly engaged or embeddedinto the raised ribs 1571 defining the spiral cutouts 1566 so that theimplant 1552 is securely held and retained in the intervertebral space1330 during articulation thereof.

In another form, a trial spacer system 1600 is shown in FIG. 88 isemployed for sizing and preparing an implantation site for an implant.The trial spacer system 1600 includes a trial spacer assembly 1750, adrill set 1900, and an insertion tool 1902. As in the embodimentdisclosed in FIG. 56, the trial spacer assembly 1750 is utilized to formfeatures in the vertebral bodies 1330, 1332 for receipt of the securingmechanism that is associated with the artificial disc implant 1752. Aprincipal difference between the trial spacer assembly 1450 of FIG. 56and the present trial spacer assembly 1750 is that present assemblyeliminates the shaft portion 1462 and integrates the drill guide 1488together with the trial spacer portion 1454. Additional features thatvary from the previous embodiment of the trial spacer assembly 1450,including the insertion tool 1902, will be described below.

The trial spacer assembly 1750 generally has a forward trial spacerportion 1754 for insertion into the intervertebral space 1330 andrearward drill guide 1788 integrated with the forward trial spacerportion 1754. The forward trial spacer portion 1754 varies little fromthe previously described embodiment in FIG. 56, and therefore will notbe described in full detail here. However, one feature notably differentin geometry from the previous embodiment is the upper stop member 1784,shown in FIG. 89 located on the upper surface of the trial spacerportion between the upper grooves 1768, 1770. In addition, both theupper grooves 1768, 1770 and the lower groove 1766 have a rearwardcounterbored portion 1904 for accommodating drill bits 1930, 1932, 1934having a forward cutting portion 1806 and a rearward counterboredportion 1808. Also, the upper and lower faces 1906, 1908 of the trialspacer portion 1754 may be skewed with respect to one another to mimicthe lordotic angle of the spine to improve the fit of the trial spacer1754. Preferably, the angle between the upper and lower faces 1906, 1908is about 5 degrees. The trial spacer assembly 1750 is preferably madewith titanium or stainless steel. In addition, the assembly ispreferably colorized using an anodization process, such that differentsized trial spacer assemblies are color coded for ease ofidentification.

The drill guide portion 1788 of the of the trial spacer assembly 1750 issimilar from the drill guide 1488 of FIG. 64, except for a few notablefeatures. For instance, the present drill guide portion 1788 replacesthe irregularly-shaped throughbore 1494 with a lower throughbore 1794similar in diameter to the upper throughbores 1792, as shown in FIG. 90.As shown in FIG. 91, the lower throughbore 1794 has an annular recessedportion 1910 for accepting the gripping mechanism 1912 of the insertiontool 1902 to allow the tool 1902 to securely attach to the trial spacerassembly 1750. Now referring to FIG. 90, the drill guide portion 1788has a rear face 1914 wherein each throughbore 1792, 1794 terminates. Onthe face 1914 adjacent to the lower throughbore 1794 are a set of threerecesses 1916, 1918 for providing three positions at which the insertertool 1902 may engage the trial spacer assembly 1750. Each recess 1916,1918 is sized to mate with a single corresponding guide pin 1920 on thebarrel 1922 of the inserter tool 1902. When the middle recess 1916 isengaged by the pin 1920 of the inserter tool 1902 (as in FIG. 91), thetrial spacer assembly 1750 is held at a neutral angle, with the verticalaxis (denoted with a “v”) of the assembly parallel with the verticalaxis of the inserter tool 1902. The two remaining recesses 1918 toeither side of the middle recess 1916 allow the user to grip the trialspacer assembly 1750 at 45 or −45 degrees with respect to the verticalaxis. This allows the surgeon to manipulate the trial spacer 1750 inmultiple positions, and gives the tool 1902 greater flexibility.Accordingly, the tool 1902 has a plurality of relative positions betweenthe tool barrel 1922 and the trial spacer assembly 1750. The drill guideportion 1788 also defines a lateral bore 1924 for providing a point ofreference for the surgeon when viewing the trial spacer 1750 usingfluoroscopy to help position the assembly 1750 once inserted into thepatient's body. A bore 1924 is used because the trial spacer assembly1750 is preferably made out of stainless steel or titanium.

Now referring to FIG. 88, each drill bit 1930, 1932, 1934 of the set1900 has identical cutting surfaces 1806, 1808 on the forward end of theshaft 1928. The forward cutting portion 1806 consists of a cuttingsurface at the tip of the bit 1796 suitable for cutting an elongategroove 1498 in the vertebra 1332, 1334 for the forward portion of thesecuring mechanism of the implant 1752. At the rear end of the firstcutting portion 1806 begins the counterbore cutting portion 1808 forcreating a counterbore in the vertebra to provide clearance for the headof the securing mechanism.

Each drill bit 1796 has a collar 1926 for providing an abutment surfaceto restrict the distance the bit 1796 may be inserted into the trialspacer assembly 1750. The collar 1926 is an enlarged portion of thedrill bit shaft 1928 and abuts the rear face 1914 of the trial spacerassembly 1750 when the drill bit 1796 is fully inserted. This keeps thesurgeon from unintentionally drilling too far and damaging surroundingtissue, bone, nerves, and other vital areas.

As shown in FIG. 88, the drill set 1900 is comprised of three drill bits1930, 1932, 1934 having shafts 1928 of differing lengths. The length ofeach shaft 1928 is different so the bits 1930-34 may be left in thedrill guide 1788 and used sequentially, from shortest to longest,without interfering with the drill. The first and shortest bit 1930 isused to create the first groove 1798 in the upper vertebra 1332, thesecond and intermediate bit 1932 to create the second groove 1798 in theupper vertebra 1332, and the third and longest bit 1934 to create thegroove 1800 in the lower vertebra 1334. This way, the first and seconddrill bits 1930, 1932 need not be removed from the trial spacer assembly1750 prior to insertion of the third drill bit 1934. Once the first andsecond drills have cut grooves 1798 into the upper vertebra 1332, theyremain in place to act as placeholders in the newly formed grooves 1798.In this manner, the drill bits 1900 help to secure the trial spacer 1750in place to prevent movement of the trial spacer assembly 1750 withrespect to the vertebrae 1332, 1334 while the other grooves are beingcut and while the inserter tool 1902 is being removed. Advantageously,no other fixation means, such as bone screws, are necessary to securethe trial spacer 1750 to the vertebrae 1332, 1334.

Now referring FIG. 92, the trial spacer inserter 1902 comprises agripping assembly 1912 connected by a barrel 1922 to a handle 1936 andan actuator in the form of a trigger 1938. As shown in FIGS. 93 and 94,the handle 1936, preferably made of a polymer, such as Radel®, has apartially hollow interior including an annular recess 1940 for acceptinga downwardly extending handle shaft 1942 having a threaded recess 1944at the bottom. A fastener 1946 affixes the handle 1936 to the downwardlyextending handle shaft 1942 by threading the fastener 1946 into thethreaded end 1944. The handle shaft 1942 is welded or otherwiseintegrated into the yoke housing 1948 of the inserter 1902. The trigger1938 is attached to an elongate trigger link 1950 at the link's lowerend with two pins 1952. The trigger link 1950 is disposed partiallywithin the interior of the handle 1936 and pivots about a hinge pin 1954which protrudes through the trigger link 1950 and is captured within thehandle 1936. At its upper end, the trigger link 1950 has an actuatinghead portion 1956 for actuating the gripping mechanism 1912.

Specifically, the head portion 1956 of the trigger link 1950 directlyengages the yoke 1958 to move it within the yoke housing 1948 to actuatethe gripping mechanism. The yoke 1958 is a cylindrical body having abore 1960 for accepting the head portion 1956 of the trigger link 1950and is directly propelled thereby. The yoke 1958 is attached to the pushrod 1962 at the rear portion of the yoke's forward end. A spring 1964disposed between the yoke 1958 and the internal end wall of the yokehousing 1948 provides a biased resistance to the trigger 1938 when theyoke 1958 is actuated by the trigger link 1950.

The yoke housing 1948 is connected to the barrel 1922, which defines aninternal bore 1960 for guiding the push rod 1962 through the barrel1922. The push rod 1962 is preferably made of a flexible material, suchas Nitinol. The push rod 1962 extends through the internal bore 1960within the barrel 1922 from the yoke 1958 to the gripping mechanism1912. The gripping mechanism 1912 includes a wedge shaped plunger 1966connected to the push rod 1962 and an expandable flared end 1968. Theflared end 1968 has a plurality of flexible tabs 1970 each having aprotrusion 1972 at the forward end of the tab 1970 for engaging therecessed portion 1910 within the lower throughbore 1794 of the trialspacer assembly 1750 as shown in FIG. 91. The tabs 1970 also have astabilizing ridge 1974 for engaging the internal surface of the lowerthroughbore 1974 to further stabilize the trial spacer assembly 1750 toprevent unwanted movement between the assembly 1750 and the insertertool 1902. The flared end 1968 is sized to fit within the lowerthroughbore 1794 when the plunger 1966 is not retracted. The flexibletabs 1970 are splayed radially outwards by the wedge-shaped plunger 1966when the plunger 1966 is pulled inwards towards the rear. When theplunger 1966 is retracted, the flexible tabs 1970 engage the internalsurfaces of the lower throughbore 1794.

The barrel 1922 includes an insertion guide 1976 disposed on the barrel1922 near the gripping mechanism 1912 for abutting the rear face 1914 ofthe drill guide portion 1788 to prevent inserting the barrel 1922 toofar into the lower throughbore 1794. In addition, the insertion guide1976 comprises a guide pin 1920 as described above for engaging therecesses 1916, 1918 in the rear face 1914 of the drill guide portion1788 to increase maneuverability and stability of the trial spacerassembly 1750.

A solid cylindrical end cap 1978 at the rear end of the tool 1902 isconnected to the yoke housing 1948 to provide a contact surface for thesurgeon to strike during insertion of the trial spacer assembly 1750.

In operation, the gripping mechanism 1912 is inserted into the lowerthroughbore 1794 of the trial spacer assembly 1750 with the trigger 1938depressed to push the plunger 1966 forward to disengage the flexibletabs 1970 of the gripping mechanism 1912. Once the inserter end is fullyinserted into the trial spacer assembly 1750, the trigger 1938 isreleased, causing the plunger 1966 to be pulled back and splaying theflexible tabs radially outward. The flexible tabs 1970 are forced intogripping engagement with the internal surfaces of the lower throughbore1794, and the guiding pin 1920 engages one of the recesses 1916, 1918 inthe rear face 1914 of the drill guide portion 1788 for providingadditional stability and control. The trial spacer 1750 is then insertedinto the intervertebral space 1330. If the spacer 1750 is theappropriate size, the surgeon will then prepare the vertebrae 1332, 1334for the implant 1752. While continuing to hold the trial spacer assembly1750 in place with the trial spacer inserter 1902, the first drill bit1930 is affixed to the drill, and then inserted into one of the upperthroughbores 1792 of the trial spacer assembly 1750. The first groove1798 is drilled. While the drill bit 1930 is still fully within thetrial spacer assembly 1750, the drill bit 1930 is released from thedrill and left in place. Next, the second intermediate drill bit 1932 isattached to the drill and the second upper groove 1798 is then drilled.Again, the second drill bit 1932 is left in place. The inserter 1902 isthen removed from the trial spacer assembly 1750. This is done bypulling the trigger 1938 to disengage the gripping mechanism 1912 andpulling the inserter 1902 away. The inserter tool 1902 is then removedand the lower groove 1800 is drilled, using the third and longest drillbit 1934. Once all of the grooves have been drilled, all three of thedrill bits 1930-34 are removed by hand. In a preferred embodiment, thecam cutting step described in FIGS. 69-71 is omitted because theartificial disc implant 1752 is provided with cutting-type cams 1846 aspreviously described. Then, to remove the trial spacer assembly 1750,the insertion tool 1902 is reinserted into the lower throughbore 1794,the trigger 1938 is released to grip the trial spacer assembly 1750, andthe assembly 1750 is pulled out using the insertion tool 1902. Thesurgical site is then preferably irrigated in preparation for insertionof the implant 1752.

The artificial disc implant 1752 of the present embodiment varies inonly a few respects compared with the artificial disc implant shown inFIGS. 72-76. For instance, the present embodiment has a different formof disc indicator member 232. The following embodiments provide tactilefeedback regarding the position of the securing mechanism to the surgeonas the securing mechanism is deployed. Because the bone is relativelysoft compared to the projections being deployed into the bone, the boneprovides little resistance to the projections as they are deployed intothe bone. Therefore, it is important to provide the surgeon with tactilefeedback so that he does not over or under deploy the projections,causing the implant 1752 to be improperly affixed to the bone. Inaddition, it is important to provide the securing mechanism withpositive retraction blocking structure. Because the vertebral boneprovides only a limited amount of resistance to the deployableprojections, the projections may be prone to retract, derotate, orotherwise begin to return to their original undeployed position overtime. Thus, retraction blocking structures are provided on the discimplant 1752 to avoid this condition.

The securing mechanism may take many forms. In one embodiment accordingto FIG. 96, the securing mechanism takes the form of a cam shaft 1816.The cam shaft 1816 has a radially extending cam projection 1979including a tactile feedback creating surface in the form of awedge-shaped camming surface 1980 adjacent the drive head 1834. Thecamming surface 1980 frictionally engages a corresponding cammingsurface 1982 disposed on the adjacent retainer member 1824 shown in FIG.97 (in a test block for demonstrative purposes with heads 1834 of thecam shafts 1816 hidden) as the cam shaft 1816 is rotated from itsundeployed starting position (on left side of FIG. 97), to a partiallydeployed position, and then to its fully deployed position 180 degreesfrom its starting position. The camming surfaces 1980 and 1982 areinclined relative to the longitudinal axis 1981 so that as the cammingsurfaces 1980, 1982 engage and cam against each other, the cam shaft1816 is shifted axially towards the anterior direction (as installed inthe spine).

This frictional interaction between the camming surfaces 1980, 1982 anda biasing force exerted by the retainer members 1824 on the cam shaft1816 caused by the deformation of the retainer members 1824 providestactile feedback to the surgeon. The deformation of the retainer membersis preferably elastic, such that the retainer members 1824 will returnto their original shape when the cam shaft 1816 is in its fully deployedposition. Alternatively, the deformation could be plastic, wherein theretainer members 1824 undergo some irreversible deformation. This isacceptable when the securing mechanism is not deployed and retractedrepeatedly.

Once the cam shaft 1816 is turned a full 180 degrees, the cam shaftcamming surface 1980 snaps into a recess 1984 formed in the adjacentretainer member 1824, due to the biasing force exerted on the cam shaft1816 by the flexed retainer members 1824. The recess 1984 and cam shaftcamming surface 1980 is formed such that the camming surface 1980becomes trapped in the recess 1984 and blocks derotation of the camshaft 1816. More specifically, the cam projection 1979 has a straight,trailing edge surface 1983 that is turned toward the straight edgesurface 1985 of recess 1984. Once the trailing edge surface 1983 clearsthe recess surface 1985, the cam surface 1980 will have traveled pastthe corresponding camming surface 1982 so that the cam surfaces 1980 and1982 are disengaged from one another. This removes the axial biasingforce that their camming engagement generates, so that the camprojection 1979 travels or snaps axially back into the recess 1984. Inthis orientation, the flat edge surfaces are in confronting relation toeach other so that the cam projection 1979 cannot be moved back out ofthe recess 1984.

Now referring to FIGS. 98 and 99, another embodiment of the securingmechanism for providing tactile feedback to the surgeon and preventingretraction of the securing mechanism is disclosed. The cam shaft 1816has a flat camming surface 1986 adjacent the drive head 1834. As shownin FIG. 99 (in a test block arrangement similar to FIG. 97), the flatcamming surface 1986 frictionally engages a corresponding cammingsurface 1988 formed in the adjacent retainer member 1824. The cammingsurfaces 1986, 1988 operate similarly to the wedge shape camming surface1980 and corresponding camming surface 1982, except that instead ofbiasing the cam shaft 1816 axially, they bias the cam shaft 1816generally vertically. As the cam shaft 1816 is rotated from its startingposition to the fully deployed position (at 180 degrees from itsundeployed starting position), the flat camming surface 1986 of the camshaft 1816 engages the corresponding camming surface 1988 of theretainer member 1824. This pushes the cam shaft 1816 generally upwardaway from the retainer members 1824, which biases the cam shaft 1816against the upwardly extending arm 1826 of the retaining members 1824,providing tactile feedback to the surgeon in the form of increasedresistance to the rotation of the cam shaft 1816 until the shaft isalmost turned a full 180 degrees. The resistance dissipates quickly asthe camming surfaces begin to disengage each other. In fact, thedeformation of the retaining members 1824 may help to propel the camshaft into a fully deployed position. This propulsion and dissipation ofresistance constitutes additional tactile feedback which varies duringthe deployment of the securing mechanism and informs the surgeon thatthe cam members 1846 are fully deployed. Once the cam shaft 1816 isturned a full 180 degrees, the flat camming surface 1986 snaps into arecess 1990 formed in the adjacent retainer member 1824, due to thegenerally vertical biasing force exerted by the flexed retainer members1824. The recess 1990 and cam shaft camming surface 1986 are formed suchthat the camming surface 1986 becomes trapped in the recess 1990 andprevents derotation of the cam shaft 1816.

More specifically, the cam projection 1987 has a straight, trailing edgesurface 1989 that is turned toward the straight edge surface 1991 ofrecess 1990. Once the trailing edge surface 1989 clears the recesssurface 1991, the cam surface 1986 will have traveled past thecorresponding camming surface 1988 so that the cam surfaces 1986 and1988 are disengaged from one another. This removes the vertical biasingforce that their camming engagement generates, so that the camprojection 1987 travels or snaps axially down into the recess 1990. Inthis orientation, the straight edge surfaces 1989, 1991 are inconfronting relation to each other so that the cam projection 1987cannot be moved back out of the recess 1990.

In another form shown in FIGS. 100 and 101, the cam shaft 1816 has adual chamfered camming surface 1992 for providing tactile feedback tothe surgeon and preventing derotation of the cam shaft 1816. In thisembodiment, a chamfered surface 1994 for providing resistive feedbackduring deployment of the cam lobes 1846 is provided on one side of thecamming surface 1992, which is engaged when the cam shaft 1816 isrotated in a clockwise direction. Another chamfered surface 1996 isprovided on the other side of the camming surface 1992 for providingresistive feedback during retraction of the cam lobes 1846, which isengaged when the cam shaft 1816 is rotated in a counterclockwisedirection. Like the embodiments described directly above, the cammingsurface 1992 engages a corresponding generally concave camming surface1998 formed in the adjacent retainer member 1824. The correspondingcamming surface 1998 is formed such that the chamfered camming surface1992 adjacent the drive head engages the corresponding camming surface1998 causing the cam shaft 1816 to bias against the retainer members1824 and provide tactile or resistive feedback as described above.Unlike the embodiments above, the cam 1816 may be manually retracted byturning the cam shaft 1816 back 180 degrees in the counterclockwisedirection. This is desirable if the surgeon wishes to adjust the implant1752 or prepare the implantation site further. Over-rotation androtation in the wrong direction is prevented by leaving a raised surface2000 on the opposite side of the corresponding camming surface 1998 suchthat it is virtually impossible to turn the cam shaft 1816 in the wrongdirection due to interference between the camming surface 1992 on thecam 1816 and the raised surface 2000.

The cam shafts 1816, cam members, lobes, or fins 1846 may take ondifferent geometries and orientations to improve performance of thesecuring mechanism. For example, the camming fins may include serrations2002, as shown in FIG. 102, divots, or recesses 2002 to promote boneyingrowth. The serrations 2002 may also help to cut the bone when the cam1816 is rotated. In addition, the camming fins 1846 may be cupped orslanted, as shown in FIG. 103, to further promote anchoring of theimplant 1752 to the vertebrae 1332, 1334. In a preferred embodiment, thecamming fins 1846 are cupped about 8 degrees. Further, as shown in FIGS.104 and 105, the camming fins 1846 may have an outside contour, suchthat shape or size of the cam fins 1846 varies from one end of the camshaft 1816 to the other. The contour may match the profile of theendplates to take advantage of the softer bone in the center of thevertebrae 1332, 1334 as opposed to the harder-denser bone at theperiphery of the vertebrae 1332, 1334. Further, the cam shafts 1816 mayhave any number of cam members 1846. In a preferred embodiment, each camshaft 1816 may have between three and five cam members 1846. Largerimplants may have five members 1846 per cam shaft 1816, while smallerimplants may have only three. The cam shafts 1816 are preferably madefrom titanium or stainless steel, and may be coated with a bone-growthpromoting substance, such as hydroxyapatite, tricalcium phosphates, orcalcium phosphates.

Cam members 1846 that cut or imbed themselves into the bone provideadvantages over other securing mechanisms. For instance, securingmechanisms that use static projections such as spikes and keels may relyon the subsidence of the bone around the securing mechanism to securethe implant. Static securing mechanisms are less desirable because theymay not properly secure the implant to the bone until the bone begins tosubside around the securing mechanism. Thus, the implant may tend tomigrate prior to bone subsidence. However, dynamic securing mechanismslike cam members 1846 with cutting surfaces 1848 actively cut into orimbed themselves into the bone, instead of relying on the subsidence ofthe bone. In this manner, dynamic securing mechanisms create a much morereliable and stable connection between the implant 1752 and the vertebra1332, 1334. These benefits translate into a more robust and reliableimplant 1752, which means quicker recovery times and increased mobilityfor the patient.

In another form, the cam shafts 1816 on the upper disc implant member1818 may be disposed at converging or diverging angles, such as shown inFIG. 106. This orientation prevents migration of the implant 1752 notonly in an anterior/posterior direction, but also substantially in thelateral direction as well. Naturally, the lower disc implant member 1822may employ such a configuration.

It should be noted that the cam shafts 1816 provide certain advantagesover other securing mechanisms, such as screws. For instance, screws donot provide a significant level of tactile feedback. It is verydifficult for a surgeon to determine how far a screw has been turned,and therefore he may over- or under-rotate the screw, increasing therisk of implant migration and failure. In addition, metal screws maydamage the implant if over-tightened. If the implant is made of arelatively soft material, such as PEEK, the metal screws will easilystrip and damage the implant if over-tightened. Moreover, a surgeon ismore likely to over-tighten a screw housed within a polymer because thescrew is so much harder than the polymer that he will not be able tofeel when the screw has been over-tightened. To alleviate this problem,the implant 1752 may be fabricated with a metal portion for housing thescrew combined with a polymer, but this greatly increases the difficultyin manufacturing the implant 1752, as well as its cost, and is thereforeless desirable. In addition, over-rotation of a screw may advance thescrew beyond its intended range of motion, and may cause it to protrudefrom the implant and cause damage to vital areas in and around thespine. Because the cams do not advance or retreat as they are rotated,there is no danger that the cams 1846 will be accidentally projectedinto other vital areas.

The disc implant 1752 according to the present embodiment has dockingfeatures for attaching with the implant insertion tool 2008, as shown inFIGS. 101, 107, and 108. The lower disc implant member 1822 has ashelf-like platform 2006 along its rear face on either side of the camshaft 1816 for providing a contact surface for the implant insertiontool 2008. Similarly, the upper disc implant member 1818 has a shelf2010 on its anterior face between the two upper cam shafts 1816 forproviding a contact surface for the insertion tool 2008. The internalfacing surfaces 1620 of both disc members 1818, 1822 each have a pair ofgenerally rectangular recesses 2012 disposed therein to accept thegripping members 2014 of the insertion tool 2008. These docking featuresare advantageous because the insertion tool 2008 manipulates the implant1752 substantially within the overall footprint of the implant 1752.This prevents trauma to the surrounding tissue and bone during insertionof the implant 1752 and removal of the inserter 2008 after the implant1752 is inserted.

An insertion tool 2008 according to the present invention is shown inFIGS. 108-113B. The insertion tool 2008 is generally comprised of ahandle portion 2016, an actuator, and a gripping mechanism 2020.Specifically, the handle portion 2016 is attached to a handle shaft2022. The handle shaft 2022 has an annular bore 2024 therethrough forslidingly housing the push rod 2026. An actuator in the form of a camlever 2018 with opposed camming surfaces is attached to the handle shaft2022 and push rod 2026 with a pin connection 2030 extending between thecamming surfaces 2028 and through opposed openings 2032 in the handleshaft 2022 and a bore 2034 in the push rod 2026. The handle shaft 2022is attached at its forward end to upper and lower housing members 2036,2038 which house the gripping mechanism 2020. A rear spring 2040surrounds push rod 2026 and is biased between a collar 2042 on thehandle shaft 2022 and the prong holder 2044. The prong holder 2044 is arectangular shaped block with four L-shaped recesses 2046 (see FIG.110), two on the upper face and two on the lower face for capturing theL-shaped anchoring ends 2048 of four prongs 2050, 2052. The prong holder2044 has a cylindrical bore 2054 extending between the front and rearface for allowing the push rod 2026 to pass therethrough. The end of thepush rod 2026 extends through a forward spring 2056, which is capturedbetween the prong holder 2044 and a compression block 2058, which isattached to the end of the push rod 2026. The compression block 2058 isa rectangular block having an aperture in the rear face for attaching tothe push rod 2026. In addition, the block 2058 has a pair of verticallyaligned bores 2060 extending laterally through the side walls of theblock 2058 for holding two pins 2062 operable to actuate the prongs2050, 2052 into a disengaged position by temporarily deforming theprongs 2050, 2052 between the two pins.

The gripping mechanism 2020 includes two upper and two lower flexibleprongs 2050, 2052 which operate in tandem with upper and lower tabs2064, 2066 for gripping and holding the disc implant 1752 (shown in FIG.111A-B). The prongs 2050, 2052 are made with a thin rectangularstainless steel shafts having a series of bends 2068, 2072. The upperprongs 2050 generally extend along the longitudinal axis of theinsertion tool 2008 and have a series of two upward sloping bends 2068so that the implant gripping end 2070 of the prong 2050 is verticallyhigher than the anchor end disposed in the prong holder 2044. The lowerprongs 2052 are shaped in a similar manner, except that they have aseries of two downward sloping bends 2072 so that the implant grippingend 2070 of the prong 2052 is vertically lower than the anchor end 2048disposed in the prong holder 2044. The upper and lower prongs 2050, 2052are paired adjacent each other and opposite the other pair along theouter lateral edges of the housing, such that the shaft 2026 andcompression block 2058 may translate between the sets of prongs 2050,2052. The upper and lower housing members 2036, 2038 have guide surfaces2074 formed in the internal surfaces for guiding and securing the prongs2050, 2052 to prevent them from becoming misaligned. The gripping ends2070 of the prongs 2050, 2052 have an L-shape for being inserted intothe recesses 2012 of the disc implant 1752.

In operation, the implant inserter tool prongs 2050, 2052 are movable invertical and longitudinal directions to engage and disengage the discimplant 1752. In the initial disengaged position shown in FIG. 112A-B,the lever 2018 is in a released position. The compression block 2058 ispushed forward by the push rod 2026. The two opposed pins 2062 extendingthrough the compression block 2058 are pushed over the sloping bends2068, 2072 in the prongs 2050, 2052, which locally deform the prongs2050, 2052 and forces the gripping ends 2070 of the prongs 2050, 2052together, effectively lowering the gripping ends 2070 of the upperprongs 2050 and raising the gripping ends 2070 of the lower prongs 2052.In this manner, the forward portion of the inserter tool 2008 may beinserted between the upper and lower disc implant members 1818, 1822. Toengage the implant 1752, the lever 2018 is pressed forwards, as shown inFIGS. 113A-B. This causes the push rod 2026 to pull the compressionblock 2058 rearwards. The opposed pins 2062 are thereby removed from thesloped portions 2068, 2072 of the prongs 2050, 2052, which allows theprongs 2050, 2052 to return to their original unflexed shape. In thismanner, the gripping ends 2070 will spread vertically apart and engagethe gripping recesses 2012 of the disc implant 1752. To provide acounteracting moment against the force imparted by the prongs 2050, 2052on the implant 1752, tabs 2064, 2066 disposed on the forward ends of thehousing members 2036, 2038 engage the implant 1752 on the shelves 2006,2010 disposed on the rear portions of the disc members 1818, 1822, asshown in FIG. 111. In addition, as the lever 2018 is pushed forward, thecompression block 2058 biases against the forward spring 2056, causingthe prong holder 2044 to be biased rearwards against the rearward spring2040. This causes the prong holder 2044 and the prongs 2050, 2052 totranslate rearwards to pull the implant 1752 tight against the forwardface of the housing members 2036, 2038. The limited range of motion ofthe lever 2018 prevents damage to the implant 1752 that may be caused byover-tightening the gripping mechanism 2020.

Once the implant 1752 is secured to the inserter 2008, the disc implant1752 is then inserted into the intervertebral space 1330. The positionof the implant 1752 may be determined using fluoroscopy to view theorientation of the implant 1752. Tantalum markers disposed in thefrontal face of both the upper and lower disc members 1818, 1822 allowthe surgeon to identify the position of the insertion end of the implant1752. In addition, the cam shafts 1816, which are also radiopaque whenmade out of titanium or stainless steel, may be used to determine theorientation of the implant 1752. After the surgeon has placed theimplant 1752 in the desired position, he releases the implant 1752 bylifting the lever 2018. The prongs 2050, 2052 are pushed forward andretracted vertically inwards, which releases the implant 1752. Thesurgeon then secures the implant 1752 in place by actuating the securingmechanism. Specifically, the surgeon turns each of the cams 1816 180degrees using a driver, thereby deploying the cam members 1846 into thebone of the upper and lower vertebrae 1332, 1334. The surgeon can feelthe resistance provided by the interaction between the camming surfacesof the cam shafts 1816 and the retainer member 1824 while deploying thecam members 1846. In this manner, he can determine when the cam members1846 have been fully deployed. In addition, the camming surfaces of thecam shafts 1816 and the retainer members 1824 will prevent the cams 1816from derotating and allowing the implant 1752 to migrate.

In a preferred embodiment, such as illustrated in FIGS. 114-134, anartificial disc device comprises an upper bearing member and lowerbearing member. In FIGS. 114-121, only the upper bearing member 3008 isshown, although an implant according to the present invention preferablyincludes both upper and lower bearing members. The lower bearing memberis preferably similar in structure to those illustrated in FIGS.122-130. An implant according to the present invention includes one ormore restraint portion(s) or structure located on one or both of thebearing members to help keep the bearing members from becoming dislodgedor migrating across the inner surface or endplate of the vertebrae (notshown) after insertion. The restraint portion may take the form of adeployable securing member 3006, which is movable from an undeployedconfiguration, wherein the restraining portion is positioned remotelyfrom the adjacent bone surface and a deployed configuration, wherein therestraining portion is positioned in contact with the adjacent bone foraffixing the implant thereto. Described in this application are varioussecuring members that can be used on the endplate facing surfaces of avertebra to restrain an implant.

In the form shown in FIGS. 114-121, an upper bearing member 3008 isshown with a single securing member 3006. The elongate groove 3007formed in the outer bearing surface 3008 f of the upper bearing member3008 shown on the right hand side in FIG. 114 is preferably replaced bya restraint portion similar to securing member 3006 to increase grippingengagement with the vertebra. Thus, the securing member 3006 shownserves as an example according to the present invention, and may belocated on other portions of an implant, alone or in combination withother securing members 3006.

The securing member 3006 in the present form has restraint portions inthe form of deployable bone engaging members 3006 a. The bone engagingmembers 3006 a are disposed on an elongate shaft 3006 b housed withinthe body of the bearing member 3008. In a preferred orientation, thesecuring member 3006 is secured within a recess 3008 b of the body ofthe bearing member 3008 by a securing member receiving portion 3008 a inthe form of a snap joint. A neck portion 3006 d of the elongate shaft3006 b is held by opposing inner surfaces 3008 c of the receivingportion 3008 a via an interference or friction fit. In this regard, thepreferred PEEK material from which the bearing members including thereceiving portion 3008 a thereof are formed provides the receivingportion 3008 a with sufficient strength and resiliency to provide asecure friction fit with the shaft portions 3006 b snap-fit therebetweenwhile allowing for the shaft portions 3006 b to be rotated to secure thebearing member 3008 to the corresponding adjacent vertebrae. Thisconfiguration is advantageous, because it requires no additionalfasteners, pins, or supports, thereby reducing parts and increasingreliability and safety of the implant.

The elongate shaft 3006 b is preferably configured with a profilesuitable for rotation. The elongate shaft is 3006 b provided with adrive head 3006 c operable to mate with an actuator, such as a driver,operable to deploy the restraint portions via rotation of the elongateshaft 3006 b. The securing member receiving portion 3008 a includes anactuator receiving portion 3008 e for receiving the actuator therein. Inthe form illustrated in FIGS. 114-121, the actuator receiving portion3008 e provides clearance for the driver to grasp the drive head 3006 c,and keeps the drive head 3006 c from protruding outside of the footprintof the implant body. This feature increases the safety and comfort ofthe implant over other known implants, because implants with projectionsthat extend outside of the implant body and especially outside of theintervertebral space can interfere with adjacent vital tissues, nerves,blood vessels, and the digestive and respiratory tracts.

The bone engaging members 3006 a take the form of lobe members that maybe deployed into engagement with the endplate of the vertebrae uponrotation of a drive head 3006 c of the elongate shaft 3006 b using theproper instrument. The lobe members 3006 a have bodies orientedgenerally transversely to a longitudinal axis of the elongate shaft 3006b. In this orientation, the lobe members 3006 a keep the implant frommigrating, particularly in the direction along the longitudinal axis.The lobe members 3006 a may include a sharpened edge for easing thedeployment of the lobe members 3006 a into the adjacent bone. The lobemembers 3006 a may include apertures or slots to encourage bone growththerethrough. In addition, the lobe members 3006 a may take a variety ofsizes and shapes. Additional examples of securing members may be foundin U.S. patent application Ser. No. 11/856,667, filed Sep. 17, 2007,which is incorporated herein in its entirety. Further, although thesecuring member 3006 is shown having three lobe members 3006 a,different numbers of bone engaging members may be implemented. Thesecuring member may be manufactured from an array of biocompatiblematerials, including, but not limited to polymers such as PEEK or metalssuch as titanium or stainless steel alloys, although radiolucentmaterials are preferred.

More specifically, the securing member 3006 includes several lobemembers 3006 a spaced along the length thereof. Initially, in anundeployed configuration, the securing member 3006 is oriented with thelobe members 3006 a oriented downwards or towards the interior of theimplant, as shown in FIGS. 115 and 116, for insertion of the implantinto the intervertebral space. The lobe members 3006 a are received inthe restraint portion recesses 3008 d formed in the upper surface 3008 fof the upper bearing member 3008. Rotating the shaft 3006 b 180 degreesvia a driver from its undeployed insertion orientation to its deployedbone-engaging orientation shifts the lobes 3006 a either into recessescut into the vertebral body, if the vertebra has been prepared prior toinsertion of the implant, or directly into the adjacent bone if thevertebra has not been prepared. In this manner, the artificial discdevice may be secured in the intervertebral space against extrusion outtherefrom during articulation of upper and lower bearing membersrelative to each other as the upper and lower vertebrae shift via anarcuate bearing interface formed between the members (see e.g., FIG.123).

Once the disc device is inserted, the restraining portions may bedeployed into the endplate to secure the artificial disc device in thedesired location between the vertebrae. In the embodiment shown in FIGS.114-121, the securing member is completely submerged within the body ofthe implant, such that the implant may be inserted without need for anypreparation of the vertebral bodies prior to insertion. Thus, thisembodiment is advantageous for ease of insertion and for reducing traumato the implant site. However, in some cases it may be preferable toimplement an implant having a securing member that protrudes outside ofthe bone engaging surface of the bearing member.

In the embodiments shown in FIGS. 122-134, the surgeon may be requiredto prepare the vertebral body to accept restraint portions that areintended to become integrated into the bone. In most cases, thispreparation involves removing bone and creating restraint accessportions typically in the form of a recess, channel, slot or profilesimilar to the restraint feature. Obviously, the size of the restraintportion will affect the size of the restraint access portion. Therefore,it is beneficial that restraint portions that interfere with the boneare suitably sized to prevent an oversized restraint access thatcompromises the vertebrae and risks vertebrae fracture. It is preferablethat both the restraint access and restraint portion have radiused edgesto reduce stress concentrations in the vertebral body.

The deployable securing member 3006, including the deployable boneengaging members 3006 a may take on different geometries andorientations to improve performance of the securing member 3006. Forexample, the lobe members 3006 a may include serrations, divots, orrecesses to promote boney ingrowth. The serrations may also help to cutthe bone when the securing member 3006 is rotated. In addition, the lobemembers 3006 a may be cupped or slanted to further promote anchoring ofthe implant to the vertebrae. Further, the lobe members 3006 a may havean outside contour, such that shape or size of the lobe members 3006 avaries from one end of the shaft 3006 b to the other. The contour maymatch the profile of the endplates to take advantage of the softer bonein the center of the vertebrae as opposed to the harder-denser bone atthe periphery of the vertebrae. Further, the shafts 3006 b may have anynumber of lobe members 3006 a. In a preferred embodiment, each shaft3006 b may have between three and five lobe members 3006 a. Largerimplants may have five members per shaft 3006 b, while smaller implantsmay have only three. The shafts 3006 b are preferably made from titaniumor stainless steel, and may be coated with a bone-growth promotingsubstance, such as hydroxyapatite, tricalcium phosphates, or calciumphosphates.

In other forms, the shaft(s) 3006 b on the upper or lower bearingmembers may be disposed at converging or diverging angles. Thisorientation prevents migration of the implant not only in ananterior/posterior direction, but also substantially in the lateraldirection as well.

The securing members 3006 of the embodiment described in FIGS. 114-121may provide tactile feedback regarding the position of the securingmember 3006 to the surgeon as the securing member 3006 is deployed.Because the bone is relatively soft compared to the projections 3006 abeing deployed into the bone, the bone provides little resistance to theprojections 3006 a as they are deployed into the bone. Therefore, it ishelpful to provide the surgeon with tactile feedback so that he does notover- or under-deploy the projections, causing the implant to beimproperly affixed to the bone. In addition, the securing member may beprovided with positive retraction blocking structure. Because thevertebral bone provides only a limited amount of resistance to thedeployable projections, the projections may be prone to retract,derotate, or otherwise begin to return to their original undeployedposition over time. Thus, retraction blocking structures may be providedon the disc implant to avoid this condition.

In another form in accordance with the present invention, anintervertebral implant 3102 with a deployable securing member 3106 isshown in FIGS. 122-126. Generally, the implant has upper and lowerbearing members 3108, 3110, each having a plurality of deployablesecuring members 3106 disposed on the outer bearing surfaces 3108 f,3110 a. Although the current embodiment is shown with a single securingmember 3106 with a plurality of restraining portions disposed on theupper bearing member 3108, a preferred embodiment has at least onesecuring member 3106 on each bearing member 3108, 3110.

The securing member 3106 of FIGS. 122-126 includes a plurality ofrestraining portions in the form of deployable plate members 3106 a.Each deployable plate member 3106 a has a head portion 3106 b and twoopposing legs 3106 c. The head portion 3106 b is preferably providedwith a blade or sharpened tip 3106 d for easing the penetration of theadjacent bone when the plate member 3106 a is deployed into engagementwith the bone. The head 3106 b also preferably has a taperedconfiguration, thickening from the tip 3106 d down towards the legs 3106c. Opposing stops 3106 e are provided at lower faces of the head portion3106 b to support the plate member 3106 a against the body of thebearing member 3108 when the plate member 3106 a is in an undeployedconfiguration. Similarly, at least one leg 3106 c is provided with astop 3106 f with an abutment surface 3106 g for interacting with anopposing abutment surface 3108 b of the securing member receivingportion 3108 a. Between the opposing legs 3106 c is a gap 3106 h forreceiving an actuator. An actuator engagement portion in the form of anarcuate interior surface 3106 i adjacent the gap 3106 h interacts withthe actuator during insertion of the actuator, which causes deploymentof the plate member 3106 a.

The deployable plate members 3106 a are each received in the securingmember receiving portion 3108 a in restraint portion recesses in theform of generally rectangular openings 3108 c (FIG. 124) in the bearingmember 3108. The openings 3108 c are disposed along the outer lateralside of the upper bearing member 3108 and are arranged in a row with thelongitudinal aspect of the openings disposed transverse to ananterior-posterior axis 3118 of the implant 3102. The securing memberreceiving portion 3108 a includes a raised ridge 3108 e that protrudesoutwardly beyond an outer bearing surface 3108 f of the bearing member3108. A cylindrical recess 3108 g is disposed in the ridge 3108 e with alongitudinal axis of the recess aligned along the anterior-posterioraxis 3118 of the bearing member 3108 for receiving the actuator in theform of an elongate plunger 3112. Plate member gaps 3108 h in the ridgeportion 3108 e are provided adjacent each opening 3108 c to provideclearance for the plate members 3106 a.

In operation, once the vertebrae have been prepared (if at all) toaccept the implant 3102, the implant 3102 is inserted into theintervertebral space using an insertion tool. The deployable securingmember 3106 is actuated by inserting the elongate plunger 3112 into thecylindrical recess 3108 g of the actuator receiving portion 3108 d, asshown in FIG. 126. The elongate plunger 3112 has a tapered tip 3112 a tofacilitate insertion thereof and gradual deployment of the deployableplate members 3106 a. During insertion of the elongate plunger 3112, thetapered tip 3112 a biases against the arcuate interior surface 3106 i,which causes the plate member 3106 a to be propelled outward towards theadjacent bone. Once the tip 3112 a progresses past the plate member 3106a, the rest of the elongate shaft of the plunger 3112 is allowed to passunderneath the interior surface 3106 i and through gap 3106 h betweenthe legs 3106 c. The elongate plunger continues into the next portion ofthe ridge 3108 e through cylindrical recess 3108 g and similarly causesthe other plate members 3106 a to deploy. Once the elongate plunger 3112is fully inserted, the enlarged head portion 3112 b of the plunger willcome into contact with an anterior facing surface 3108 n of the ridgeportion 3108 e, which keeps the plunger 3112 from being inserted toofar. Stop 3106 f keeps the plate members 3106 a from becoming loose orfrom being overextended via contact between abutment surface 3106 g andopposing abutment surface 3108 b. In the aforementioned configuration,the plate members are deployed straight up or linearly into thevertebrae, without any rotational displacement of the plate members 3106a. This embodiment is advantageous because the restraining portions donot pull the implant 3102 further into the intervertebral space, whichcan bring the implant out of the desired position, or cause trauma tothe surrounding tissue and blood vessels. The plate members 3106 a areallowed to be retracted by removing the plunger from the receivingportion 3108 a.

The lateral orientation (i.e., transverse to the anterior-posterioraxis) of the plate members 3106 a is advantageous for providing superiorresistance to migration in the anterior or posterior direction of theimplant. However, the plate members 3106 a may be oriented in otherconfigurations.

The following description of the general features of a preferredembodiment of an intervertebral implant according to the presentinvention is described with respect to the embodiment in FIGS. 122-126.However, the general features described below may be implemented in anyof the embodiments described herein.

It is preferred that the footprint of the artificial disc devices hereinbe similar to the footprint of the endplate although generally smallerto fit within the intervertebral space. The outer bearing surfaces 3108f are preferably contoured to match the contour of the endplates. Forexample, if the surgeon prepares the endplates to be flat, it ispreferred that the outer bearing surfaces 3108 f, 3110 a are also flat.Likewise, if the endplates are prepared to be concave, it is preferredthat the outer bearing surfaces 3108 f, 3110 a are similarly convex. Itshould be noted that endplates that are concave will generally retainthe artificial disc device better since the device becomes cuppedbetween the vertebrae.

FIG. 122 shows an artificial disc implant 3102 with upper and lowerbearing members 3108, 3110 having a bearing interface 3114 therebetweenthat allows the members 3108, 3110 to shift or articulate relative toeach other when implanted and secured in an intervertebral space. Thebearing interface 3114 includes concave recess 3108 i (FIG. 123) formedin the inner or lower surface 3108 p of the upper bearing member 3108and a substantially convex portion 3110 b that projects up from inner orupper surface 3110 f of the lower bearing member 3110. Although notpreferred, the concave and convex portions 3108 i, 3110 b may beswitched such that the upper bearing member 3108 may alternativelycomprise the convex portion 3110 b. The securing members according tothe present invention may be utilized with unitary implants, such asspinal cages and spacers, as well as multi-piece implants, such as themotion-preserving intervertebral implants disclosed in the drawings.

The convex portion 3110 b comprises a convex articulation surface 3110c, and the concave portion 3108 i comprises a concave articulationsurface 3108 j. It is preferred that the articulation surfaces 3110 cand 3108 j have substantially matching geometries or radii of curvaturealthough some mismatch of curvature may be desired to provide acombination of rolling and sliding motion to occur between thearticulation surfaces 3110 c and 3108 j. U.S. Provisional Application61/050,612 filed May 5, 2008 discloses a “ball-in-bowl” configurationfor the articulation surfaces, and is hereby incorporated by referencein its entirety. In particular, the concave articulation surface 3108 jmay have two different radii of curvature, such that one portion of theconcave articulation surface 3108 j has a first radius of curvature, anda second portion of the concave articulation surface 3108 j has asecond, larger radius of curvature. The first radius of curvature ispreferably the same as the radius of curvature of the convexarticulation surface 3110 c, such that rotational sliding may occurbetween the articulation surfaces 3108 j, 3110 c. When the joint isextended, the concave articulation surface 3108 j is allowed totranslate slightly due to the mismatch in curvature between the firstradius of curvature of the convex articulation surface 3110 c and thesecond, larger radius of curvature of the concave articulation surface3108 j. This configuration allows for a greater range of motion and amore natural movement of the joint.

As discussed above, the geometries may be complex in nature butpreferably are ball and socket style. The convex portion 3110 b andconcave portion 3108 i may extend substantially to the outer perimeterof the bearing member 3108, 3110 as illustrated in FIGS. 122 and 123, ormay be formed, typically with a smaller radius of curvature inward apredetermined distance from the outer perimeter of the bearing member3108, 3110. Each bearing member 3108, 3110 is preferably manufacturedfrom PEEK (polyetheretherketone) or fiber reinforced PEEK or otherbiocompatible polymer combination or radiolucent material demonstratingvery low surface wear in high repetition wear testing.

The disc implant 3102 according to the present embodiment has dockingfeatures for attaching the implant 3102 to an insertion tool. The lowerbearing member 3110 has a shelf-like platform 3110 d along its anteriorface for providing a contact surface for the implant insertion tool.Similarly, the upper bearing member 3108 has a shelf 3108 k on itsanterior face for providing a contact surface for the insertion tool.The internal facing surfaces 3108 p, 3110 f of both bearing members3108, 3110 each have a pair of generally rectangular recesses 3108 m,3110 e disposed thereon to accept gripping members of the insertiontool. Two of the gripping members, prongs 3116, are shown with theimplant 3102 for reference. The prongs 3116 engage the upper bearingmember 3108 within recesses 3108 m during insertion of the implant 3102.Preferably, two additional prongs are provided with the insertion toolfor engaging with recesses 3110 e to work in tandem with prongs 3116.These docking features are advantageous because the insertion toolmanipulates the implant 3102 substantially within the overall footprintof the implant 3102. This prevents trauma to the surrounding tissue andbone during insertion of the implant 3102 and removal of the inserterafter the implant 3102 is inserted.

Once the implant 3102 is secured to the inserter, the disc implant 3102is then inserted into the intervertebral space. The position of theimplant 3102 may be determined using fluoroscopy to view the orientationof the implant 3102. Tantalum markers 3108 q, 3110 g (FIG. 124) disposedin the posterior face of both the upper and lower bearing members 3108,3110 allow the surgeon to identify and position the posterior end of theimplant 3102. In addition, the securing member(s) 3106, which are alsoradiopaque when made out of titanium or stainless steel, may be used todetermine the orientation of the implant 3102.

In another form in accordance with the present invention illustrated inFIGS. 127-130, an intervertebral implant 3202 with a deployable securingmember is disclosed. The implant body is similar to that of theembodiment shown in FIGS. 122-126. However, the securing member iscomprised of deployable arms 3206 a which may be rotated about a pivotinto engagement with the bone. The arms 3206 a are deployed via anelongate plunger 3212 similar to that of the embodiment disclosed inFIGS. 127-130. The deployable arms are preferably rotatable about ananterior-posterior axis such that the deployable arms 3206 a aredisposed transversely to the anterior-posterior axis and translationthereof into a deployed position does not cause shifting of the implant3202.

The securing member is provided with three deployable arms 3206 a havingbone engaging head portions 3206 b. The head portion 3206 b preferablyhas a sharpened outer edge 3206 c for easing penetration of the headportion 3206 b into the bone. The head portions 3206 b have a generallyarcuate profile, with a convex outer edge 3206 c and a concave innersurface 3206 d for engaging with the arcuate outer surface of theelongate plunger 3212. Each head portion 3206 b is connected to atransverse shaft 3206 e via a neck portion 3206 f. The transverse shaft3206 e is cylindrically shaped for being pivotally captured withinsimilarly-shaped channel 3208 b. The transverse shaft 3206 e is heldwithin the channel 3208 b with a friction fit so that no additionalfasteners or pieces are required to connect the restraining portions tothe implant 3202. This construction simplifies manufacture and assembly,and increases the robustness of the implant. Because intervertebralimplants in particular may be very small in many applications, it isdesirable for such implants to have few components. For example, acervical disc implant may only be 5 mm high. Thus, these kinds ofimplants must have components that are sturdy and robust enough to befunctional on a very small scale.

The securing member receiving portion 3208 a has a similar configurationto that of the embodiment described in FIGS. 122-126. A cylindricalridge portion 3208 e protrudes outwards from the outer bearing surface3208 f and contains a cylindrical recess 3208 g for receiving theelongate plunger 3212. Lateral channels 3208 h disposed in the bearingmember and the cylindrical ridge portion 3208 e extend transversely tothe cylindrical recess 3208 g for receiving the deployable arms 3206 a.The lateral channels 3208 h are in communication with channel 3208 b.When the deployable arms 3206 a are configured within the lateralchannels 3208 h in an undeployed orientation, the arms 3206 a remainwithin the profile of the bearing member and the ridge 3208 e for easeof insertion of the implant into the intervertebral space.

To actuate and deploy the deployable arms 3206 a, the plunger 3212 isinserted into the cylindrical recess 3208 g. The tapered tip 3212 ainteracts with the concave inner surface 3206 d of the deployable arm3206 a, gradually biasing the arm 3206 a upward, causing the arm 3206 ato rotate about the transverse shaft portion 3206 e. The deployable arm3206 a is deployed fully to its maximum height once the plunger tipextends beyond the concave inner surface 3206 d, such that thedeployable arm 3206 a rests on top of and is supported by the shaft 3212b of the plunger 3212. As shown in FIGS. 129 and 130, the deployablearms protrude substantially above the ridge 3208 e such that they areoperable to engage with the adjacent bone for fixing the implant to thevertebra.

In another form in accordance with the present invention, anintervertebral implant 3302 having a deployable securing member 3306 foraffixing the implant to the adjacent vertebra is disclosed in FIGS.131-134. In the present form, the securing member 3306 a takes the formof a deformable or bendable elongate member 3306 a that may be insertedinto the securing member receiving portion 3308 a and bent into a formcausing bone engaging projections to engage with the adjacent vertebra.

The bendable elongate member 3306 a is preferably a flat elongate memberhaving a longitudinal length between its ends and a width. The elongatemember 3306 a has a leading end 3306 b with an enlarged width that isinserted first into the receiving portion 3308 a. A trailing end 3306 cis provided with a transverse tab portion 3306 d transverse to thelongitudinal length thereof for manipulating the elongate member 3306 aand providing a stop to keep the elongate member 3306 a from beinginserted too far into the intervertebral space. The trailing end 3306 cis also provided with a guide portion 3306 e having an enlarged widthfor guiding the elongate member 3306 a within the insertion instrument3314 and the securing member receiving portion 3308 a. In addition, acentral guide portion 3306 f is positioned between the two ends forguiding the elongate member 3306 a. In between either end 3306 b, 3306 cand the central guide portion 3306 f is a bending zone 3306 g which isconfigured for being bent during insertion of the elongate member 3306 aand protruding upwardly or outwardly into engagement with the adjacentbone. The bending zone 3306 g preferably includes perforations orweakened portions 3306 h to promote bending at a predetermined locationon the elongate member 3306 a. In a preferred embodiment, the bendingzones 3306 g include a preformed protrusion or spike 3306 i which lieswithin the elongate member prior to bending thereof. When the elongatemember 3306 a is bent, the bending zones are forced into an inverse Vshape, causing the spike 3306 i to be deployed upwards into the adjacentbone. Although the elongate member 3306 a is shown with two bendingzones 3306 g and spikes 3306 i, the elongate member 3306 a may beprovided with different numbers of bending zones and spikes. Althoughthe bendable elongate member has portions bent into a V shape, othershapes and configurations are contemplated.

The securing member receiving portion 3308 a takes the form of agenerally U-shaped channel 3308 b disposed along a lateral edge on theupper bearing member 3308. The channel 3308 b has opposing side walls3308 c, 3308 d and a bottom surface 3308 e extending between the twoside walls 3308 c, 3308 d. Extending between the side walls 3308 c, 3308d are restraining members in the form of pins 3308 f. The pins 3308 fare operable to restrain the elongate bending member 3306 a from bendingat predetermined locations. Pins 3308 f are preferably cylindrical orhave radiused edges to prevent stress concentrations on the bendingmember 3306 a and to reduce friction thereon during bending. Thus, thepins are located in positions corresponding to positions on the elongatebending member 3306 a that are to remain unbent. The weakened portions3306 h on the elongate member 3306 a are preferably aligned with thepins 3308 f, such that when the bending member is inserted into thereceiving portion 3308 a, the bending member will bend in the open areasbetween the pins 3308 f. As shown in FIG. 124, the pins 3308 f arepositioned above the bottom surface 3308 e such that the elongate member3306 a is held relatively snug therebetween. The channel 3308 b has anend wall 3308 j operable to provide a stop for the bending member 3306a, as well as a surface to compress the bending member 3306 a against tocause bending of the bending zones 3306 g and deployment of spikes 3306i.

The insertion instrument 3314 comprises a generally C-shaped housingwith opposing arms 3314 a, 3314 b to provide opposing grooves 3314 c,3314 d in which the bending member may be inserted for guiding thebending member into the securing member receiving portion. The widenedends 3306 b, 3306 c and central portion 3306 f fit within the grooves3314 c, 3314 d. The transverse tab portion 3306 d is sized andconfigured to fit between the opposing arms 3314 a, 3314 b such that itmay pass therebetween. This way, the bending member 3306 a may be pushedinto the receiving portion via the transverse tab portion 3306 d. Theinsertion instrument 3314 is also provided with an extended lip 3314 eon the insertion end for providing the bending member 3306 a withadditional support to prevent bending of the member 3306 a as it leavesthe insertion instrument 3314 and prior to reaching the first pin 3308 fat the entrance of the channel 3308 b at the anterior side of theimplant 3302.

In operation, the implant 3302 is first inserted into the preparedintervertebral space via an implant insertion instrument, which includesprongs 3316 which grasp the implant 3302 in opposing recesses on theinner facing surface of the upper bearing member 3308, as shown in FIG.134. Next, the bending member 3306 a is slid into the grooves 3314 c,3314 d of the insertion instrument as shown in FIG. 132. Then, theinsertion instrument 3314 is positioned adjacent the receiving portion3308 a such that the elongate member 3306 a is aligned with the channel3308 b. The bending member 3306 a is then pushed into the channel 3308 bbetween the pins 3308 f and the bottom surface of the channel 3308 e viathe transverse tab portion 3306 d. Once the insertion end 3306 b of thebending member 3306 a reaches the abutment surface 3308 j, furtherinsertion of the bending member 3306 a will cause compression and thebending member 3306 a will begin to bend or deform. This deformationbegins at the weakened portions 3306 h and causes the bending zones 3306g to deform upwards into engagement with the adjacent bone. As thebending zone 3306 g begins to bend at its peak, the barb or spike 3306 iwill be deployed upwards into the bone. Once the bending member 3306 ahas been fully inserted into the receiving portion, the insertioninstrument 3314 may be removed from the implant site. Further details ofthe preparation of the vertebrae, insertion procedure and insertion toolmay be found in U.S. patent application Ser. No. 11/856,667, which isincorporated by reference herein.

The securing member receiving portion 3308 a for the elongate bendingmember 3306 a is shown in FIGS. 131-134 in one location on the implant;however, it is contemplated that the upper and lower members 3308, 3310may include securing members 3306 in more than one location. Further,all of the securing members shown and described herein may beimplemented together with different types of securing members, such asthose shown and described above or other securing members andrestraining members known in the art. However, in a preferred form, animplant according to the present invention comprises two securingmembers of similar configurations on each bearing member.

In other forms of the invention, the implant may comprise apharmacological agent used for treating various spinal conditions,including degenerative disc disease, spinal arthritis, spinal infection,spinal tumor and osteoporosis. Such agents include antibiotics,analgesics, anti-inflammatory drugs, including steroids, andcombinations thereof. Other such agents are well known to the skilledartisan. These agents are also used in therapeutically effectiveamounts. Such amounts may be determined by the skilled artisan dependingon the specific case.

The pharmacological agents, if any, are preferably dispersed within theimplant for in vivo release. The pharmacological agents may be dispersedin the spacer by adding the agents to the implant when it is formed, bysoaking a formed implant in an appropriate solution containing theagent, or by other appropriate methods known to the skilled artisan. Inother forms of the invention, the pharmacological agents may bechemically or otherwise associated with the implant. For example, theagents may be chemically attached to the outer surface of the implant.

Although the securing members and insertion tools have been describedwith reference to a disc replacement implant, the securing members andtools may be easily adapted for use with other artificial implants, suchas fusion promoting implants, including vertebral body replacements,spinal cages, and the like. In addition, the invention described hereinmay also be applied to other motion preserving implants, such as thosewith articulating surfaces, including nucleus replacement implants.Moreover, the securing members, insertion tools, and methods describedherein may be implemented in other weight-bearing joint implants, suchas ankle, knee, or hip joint implants.

While the invention has been described with respect to specific examplesincluding presently preferred modes of carrying out the invention, thoseskilled in the art will appreciate that there are numerous variationsand permutations of the above described systems and techniques that fallwithin the spirit and scope of the invention as set forth in the claims.

What is claimed is:
 1. A tool for inserting an intervertebral implantinto an intervertebral space between adjacent vertebrae, comprising: atool body having a longitudinal tool axis; a proximal handle portion ofthe tool body; an actuator operably connected to the tool body; firstand second pairs of laterally adjacent shiftable prongs having elongatebodies and each pair having a prong with a superiorly extending distalprojection and a laterally adjacent prong with an inferiorly extendingdistal projection, the superiorly and inferiorly extending distalprojections extending in respective superior and inferior directionsalong a vertical axis orthogonal to the longitudinal axis, the first andsecond pairs of shiftable prongs disposed at a distal end of the toolbody with each pair of shiftable prongs spaced laterally from thelongitudinal axis and the other pair of shiftable prongs; wherein oneprong of each of the pairs is operably connected to the other laterallyadjacent prong of the same pair of laterally adjacent prongs and to theactuator to shift the prongs between a non-engaging configuration,wherein the projections of the prongs are positioned for being out ofengagement with the intervertebral implant, and an engagingconfiguration, wherein the superiorly extending distal projection of oneprong of each pair shifts superiorly and the inferiorly extending distalprojection of the other laterally adjacent prong of each pair shiftsinferiorly for engaging with the intervertebral implant for manipulationand insertion thereof into the intervertebral space.
 2. The toolaccording to claim 1, wherein each of the prongs comprise a distalimplant engaging end portion having a distally extending portion and oneof the superiorly and inferiorly extending distal projections thatextend transversely from the distally extending portion for engagingwith the intervertebral implant.
 3. The tool according to claim 1,wherein the prong of each pair having the superiorly extending distalprojection is located laterally outwardly relative to the longitudinaltool axis from the other adjacent prong of each pair having theinferiorly extending distal projection.
 4. The tool according to claim1, further comprising a plurality of tab members that project distallyfrom the distal end of the tool body disposed laterally between thefirst and second pairs of shiftable prongs for engaging with andgripping the implant in combination with the shiftable prongs.
 5. Thetool according to claim 1, wherein the prongs in the non-engagingconfiguration have a compact configuration wherein the superiorly andinferiorly extending distal projections of each pair of laterallyadjacent prongs are positioned side-by-side, and the prongs in theengaging configuration have an extended configuration wherein thesuperiorly and inferiorly extending distal projections of each pair oflaterally adjacent prongs are vertically spaced from each other.
 6. Thetool according to claim 1, wherein the first and second pairs ofshiftable prongs are laterally spaced apart from the longitudinal toolaxis and disposed on opposite lateral sides of the tool body from oneanother.
 7. The tool according to claim 1, wherein each of the prongbodies include a camming surface spaced proximally from the distalprojection of the prong and the tool further comprises: atransversely-oriented camming member operably connected to the actuatorand operable to biasingly engage the camming surface of at least one ofthe prongs of each pair for shifting the prongs between the non-engagingand engaging configurations.
 8. The tool according to claim 7, whereineach prong body extends along a longitudinal prong axis and the cammingsurface of each prong body is inclined relative to the longitudinalprong axis.
 9. An implant and tool combination for inserting an implantwithin an intervertebral space between adjacent vertebrae, comprising:an intervertebral disc implant; an upper bearing member of theintervertebral disc implant having a body, an outer facing bearingsurface, and an inner facing surface; a lower bearing member of theintervertebral disc implant having a body, an outer facing bearingsurface, and an inner facing surface; an articulation interface formedbetween portions of the inner facing surfaces of the upper and lowerbearing members for allowing relative movement therebetween; toolreceiving recessed openings formed in the inner facing surface of eachof the upper and lower bearing members; a docking portion of the outerfacing bearing surface of at least one of the upper and lower bearingmembers for receiving a complimentary tab member of a tool; a tool forholding and inserting the intervertebral disc implant; a tool body ofthe tool having proximal and distal ends and a longitudinal axisextending therebetween; first and second pairs of laterally adjacentshiftable prongs disposed at the distal end of the tool body, the prongshaving elongate bodies wherein one prong of each pair includes asuperiorly extending distal projection and the other laterally adjacentprong of the same pair includes an inferiorly extending distalprojection, the superiorly and inferiorly extending distal projectionsextending in respective superior and inferior directions along avertical axis orthogonal to the longitudinal axis, the first and secondpairs of prongs sized and configured to shift between a non-engagingconfiguration, wherein the prongs are positioned for being out ofengagement with the intervertebral implant, and an engagingconfiguration, wherein the superiorly extending distal projection of oneprong of each pair shifts superiorly and the inferiorly extending distalprojection of the other laterally adjacent prong of each pair shiftsinferiorly for being received in the tool receiving recessed openingsfor manipulating and inserting the bearing members into theintervertebral space; and a tab member at the distal end of the toolbody configured to be received by the docking portion causing the distalprojections of the prongs to be positioned for being shifted inferiorlyand superiorly to fit in the tool receiving recessed openings of theupper and lower bearing members.
 10. The combination of claim 9, whereinthe docking portion is recessed below the outer facing bearing surfaceof the at least one of the upper and lower bearing members, and the tooltab member for engaging with the docking portion is sized and configuredsuch that tab member does not extend above the outer facing bearingsurface surrounding the recessed docking portion with the tab memberreceived by the docking portion.
 11. The combination of claim 10,wherein the docking portion includes shelf-like recesses disposed on aproximal portion of the outer facing bearing surfaces.
 12. The toolaccording to claim 4, wherein the plurality of tab members comprise anupper tab member and first and second lower tab members, the first andsecond lower tab members being laterally spaced apart from one another.13. The tool according to claim 9, wherein the first and second pairs ofshiftable prongs are laterally spaced apart from the longitudinal axisand from one another.
 14. The tool according to claim 9, wherein theupper and lower bearing members include docking portions, and the tabmember of the tool comprises an upper implant engagement tab member forengaging with the docking portion of the upper bearing member, and thetool further comprises first and second lower implant engagement tabmembers for engaging with the docking portion of the lower bearingmember, the first and second lower implant engagement tab members beinglaterally spaced apart from one another.
 15. The tool according to claim9, wherein each prong body includes a camming surface spaced proximallyfrom the distal projection of the prong and the tool further comprises:a transversely oriented camming member operable to biasingly engage thecamming surface of at least one of the prongs of each pair for shiftingthe prongs between the non-engaging and engaging configurations.
 16. Thetool according to claim 15, wherein each prong body extends along alongitudinal prong axis and the camming surface of each prong body isinclined relative to the longitudinal prong axis.